{"id":113706,"date":"2026-10-07T07:42:50","date_gmt":"2026-10-06T23:42:50","guid":{"rendered":"https:\/\/www.wsisp.com\/helps\/113706.html"},"modified":"2026-10-07T07:42:50","modified_gmt":"2026-10-06T23:42:50","slug":"uva-12656-almost-palindrome","status":"publish","type":"post","link":"https:\/\/www.wsisp.com\/helps\/113706.html","title":{"rendered":"UVa 12656 Almost Palindrome"},"content":{"rendered":"<h3>\u9898\u76ee\u63cf\u8ff0<\/h3>\n<p>\u7ed9\u5b9a\u4e00\u884c\u6587\u672c&#xff0c;\u627e\u51fa\u5176\u4e2d\u6700\u957f\u7684 \u201c\u51e0\u4e4e\u56de\u6587\u201d \u5b50\u4e32\u3002\u4e00\u4e2a\u5b57\u7b26\u4e32 <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">SS<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.6833em\"><\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0576em\">S<\/span><\/span><\/span><\/span><\/span> \u88ab\u79f0\u4e3a \u201c\u51e0\u4e4e\u56de\u6587\u201d &#xff0c;\u5982\u679c\u6ee1\u8db3&#xff1a;<\/p>\n<li><span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">SS<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.6833em\"><\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0576em\">S<\/span><\/span><\/span><\/span><\/span> \u4ee5\u5b57\u6bcd\u5f00\u5934\u5e76\u4ee5\u5b57\u6bcd\u7ed3\u5c3e&#xff1b;<\/li>\n<li>\u5c06 <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">SS<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.6833em\"><\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0576em\">S<\/span><\/span><\/span><\/span><\/span> \u4e2d\u6240\u6709\u975e\u5b57\u6bcd\u5b57\u7b26\u5220\u9664\u5e76\u5c06\u6240\u6709\u5b57\u6bcd\u8f6c\u4e3a\u5c0f\u5199\u540e\u5f97\u5230 <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">a(S)a(S)<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 1em;vertical-align: -0.25em\"><\/span><span class=\"mord mathnormal\">a<\/span><span class=\"mopen\">(<\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0576em\">S<\/span><span class=\"mclose\">)<\/span><\/span><\/span><\/span><\/span> &#xff0c;\u5c06 <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">a(S)a(S)<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 1em;vertical-align: -0.25em\"><\/span><span class=\"mord mathnormal\">a<\/span><span class=\"mopen\">(<\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0576em\">S<\/span><span class=\"mclose\">)<\/span><\/span><\/span><\/span><\/span> \u53cd\u8f6c\u540e\u5f97\u5230 <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">b(S)b(S)<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 1em;vertical-align: -0.25em\"><\/span><span class=\"mord mathnormal\">b<\/span><span class=\"mopen\">(<\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0576em\">S<\/span><span class=\"mclose\">)<\/span><\/span><\/span><\/span><\/span> &#xff0c;\u4e24\u8005\u5728\u6700\u591a <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">2k2k<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.6944em\"><\/span><span class=\"mord\">2<\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0315em\">k<\/span><\/span><\/span><\/span><\/span> \u4e2a\u4f4d\u7f6e\u4e0a\u5b57\u7b26\u4e0d\u540c\u3002<\/li>\n<p>\u4f8b\u5982&#xff0c;\u5f53 <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">k&#061;1k &#061; 1<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.6944em\"><\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0315em\">k<\/span><span class=\"mspace\" style=\"margin-right: 0.2778em\"><\/span><span class=\"mrel\">&#061;<\/span><span class=\"mspace\" style=\"margin-right: 0.2778em\"><\/span><\/span><span class=\"base\"><span class=\"strut\" style=\"height: 0.6444em\"><\/span><span class=\"mord\">1<\/span><\/span><\/span><\/span><\/span> \u65f6&#xff0c;&#034;Race cat&#034; \u662f\u51e0\u4e4e\u56de\u6587&#xff0c;\u56e0\u4e3a <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">a(S)&#061;&#034;racecat&#034;a(S) &#061; \\\\text{&#034;racecat&#034;}<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 1em;vertical-align: -0.25em\"><\/span><span class=\"mord mathnormal\">a<\/span><span class=\"mopen\">(<\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0576em\">S<\/span><span class=\"mclose\">)<\/span><span class=\"mspace\" style=\"margin-right: 0.2778em\"><\/span><span class=\"mrel\">&#061;<\/span><span class=\"mspace\" style=\"margin-right: 0.2778em\"><\/span><\/span><span class=\"base\"><span class=\"strut\" style=\"height: 0.6944em\"><\/span><span class=\"mord text\"><span class=\"mord\">&#034;racecat&#034;<\/span><\/span><\/span><\/span><\/span><\/span> &#xff0c;<span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">b(S)&#061;&#034;tacecar&#034;b(S) &#061; \\\\text{&#034;tacecar&#034;}<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 1em;vertical-align: -0.25em\"><\/span><span class=\"mord mathnormal\">b<\/span><span class=\"mopen\">(<\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0576em\">S<\/span><span class=\"mclose\">)<\/span><span class=\"mspace\" style=\"margin-right: 0.2778em\"><\/span><span class=\"mrel\">&#061;<\/span><span class=\"mspace\" style=\"margin-right: 0.2778em\"><\/span><\/span><span class=\"base\"><span class=\"strut\" style=\"height: 0.6944em\"><\/span><span class=\"mord text\"><span class=\"mord\">&#034;tacecar&#034;<\/span><\/span><\/span><\/span><\/span><\/span> &#xff0c;\u5b83\u4eec\u6b63\u597d\u6709 <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">22<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.6444em\"><\/span><span class=\"mord\">2<\/span><\/span><\/span><\/span><\/span> \u4e2a\u4f4d\u7f6e\u4e0d\u540c\u3002<\/p>\n<h3>\u8f93\u5165\u683c\u5f0f<\/h3>\n<p>\u8f93\u5165\u5305\u542b\u6700\u591a <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">2525<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.6444em\"><\/span><span class=\"mord\">25<\/span><\/span><\/span><\/span><\/span> \u4e2a\u6d4b\u8bd5\u7528\u4f8b\u3002\u6bcf\u4e2a\u6d4b\u8bd5\u7528\u4f8b\u4e24\u884c&#xff1a;<\/p>\n<ul>\n<li>\u7b2c\u4e00\u884c\u662f\u4e00\u4e2a\u6574\u6570 <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">kk<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.6944em\"><\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0315em\">k<\/span><\/span><\/span><\/span><\/span>&#xff08;<span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">0\u2264k\u22642000 \\\\le k \\\\le 200<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.7804em;vertical-align: -0.136em\"><\/span><span class=\"mord\">0<\/span><span class=\"mspace\" style=\"margin-right: 0.2778em\"><\/span><span class=\"mrel\">\u2264<\/span><span class=\"mspace\" style=\"margin-right: 0.2778em\"><\/span><\/span><span class=\"base\"><span class=\"strut\" style=\"height: 0.8304em;vertical-align: -0.136em\"><\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0315em\">k<\/span><span class=\"mspace\" style=\"margin-right: 0.2778em\"><\/span><span class=\"mrel\">\u2264<\/span><span class=\"mspace\" style=\"margin-right: 0.2778em\"><\/span><\/span><span class=\"base\"><span class=\"strut\" style=\"height: 0.6444em\"><\/span><span class=\"mord\">200<\/span><\/span><\/span><\/span><\/span>&#xff09;&#xff1b;<\/li>\n<li>\u7b2c\u4e8c\u884c\u662f\u4e00\u4e2a\u5b57\u7b26\u4e32&#xff0c;\u957f\u5ea6\u4e0d\u8d85\u8fc7 <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">10001000<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.6444em\"><\/span><span class=\"mord\">1000<\/span><\/span><\/span><\/span><\/span> \u4e2a\u5b57\u7b26&#xff08;\u4e0d\u542b\u6362\u884c\u7b26&#xff09;&#xff0c;\u81f3\u5c11\u5305\u542b\u4e00\u4e2a\u5b57\u6bcd\u3002\u5b57\u7b26\u4e32\u53ea\u5305\u542b\u5b57\u6bcd\u3001\u7a7a\u683c\u548c\u5176\u4ed6\u53ef\u6253\u5370\u5b57\u7b26&#xff08;\u5982 , \u6216 . \u7b49&#xff09;&#xff0c;\u4e14\u4e0d\u4f1a\u4ee5\u7a7a\u767d\u5b57\u7b26\u5f00\u5934\u3002<\/li>\n<\/ul>\n<h3>\u8f93\u51fa\u683c\u5f0f<\/h3>\n<p>\u5bf9\u4e8e\u6bcf\u4e2a\u6d4b\u8bd5\u7528\u4f8b&#xff0c;\u8f93\u51fa\u4e00\u884c&#xff0c;\u683c\u5f0f\u4e3a Case x: L P &#xff0c;\u5176\u4e2d <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">xx<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.4306em\"><\/span><span class=\"mord mathnormal\">x<\/span><\/span><\/span><\/span><\/span> \u662f\u6d4b\u8bd5\u7528\u4f8b\u7f16\u53f7&#xff08;\u4ece <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">11<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.6444em\"><\/span><span class=\"mord\">1<\/span><\/span><\/span><\/span><\/span> \u5f00\u59cb&#xff09;&#xff0c;<span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">LL<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.6833em\"><\/span><span class=\"mord mathnormal\">L<\/span><\/span><\/span><\/span><\/span> \u662f\u6700\u957f\u51e0\u4e4e\u56de\u6587\u5b50\u4e32\u7684\u957f\u5ea6&#xff0c;<span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">PP<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.6833em\"><\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.1389em\">P<\/span><\/span><\/span><\/span><\/span> \u662f\u8be5\u5b50\u4e32\u7684\u8d77\u59cb\u4f4d\u7f6e&#xff08;\u4ece <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">11<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.6444em\"><\/span><span class=\"mord\">1<\/span><\/span><\/span><\/span><\/span> \u5f00\u59cb\u8ba1\u6570&#xff09;\u3002\u5982\u679c\u6709\u591a\u4e2a\u957f\u5ea6\u76f8\u540c\u7684\u6700\u957f\u5b50\u4e32&#xff0c;\u8f93\u51fa\u8d77\u59cb\u4f4d\u7f6e\u6700\u5c0f\u7684\u90a3\u4e2a\u3002<\/p>\n<h3>\u6837\u4f8b<\/h3>\n<p>\u8f93\u5165<\/p>\n<p>1<br \/>\nWow, it is a Race cat!<br \/>\n0<br \/>\nabcdcfg<br \/>\n0<br \/>\nKitty: Madam, I&#039;m adam.<\/p>\n<p>\u8f93\u51fa<\/p>\n<p>Case 1: 8 3<br \/>\nCase 2: 1 1<br \/>\nCase 3: 15 8<\/p>\n<h3>\u9898\u76ee\u5206\u6790<\/h3>\n<p>\u672c\u9898\u7684\u6838\u5fc3\u662f&#xff1a;\u5728\u7ed9\u5b9a\u6587\u672c\u4e2d&#xff0c;\u627e\u51fa\u4e00\u4e2a\u5b50\u4e32&#xff0c;\u5176\u5b57\u6bcd\u5e8f\u5217\u4e0e\u53cd\u8f6c\u540e\u7684\u5b57\u6bcd\u5e8f\u5217\u5728\u76f8\u540c\u4f4d\u7f6e\u4e0a\u7684\u4e0d\u540c\u5b57\u7b26\u4e2a\u6570\u4e0d\u8d85\u8fc7 <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">2k2k<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.6944em\"><\/span><span class=\"mord\">2<\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0315em\">k<\/span><\/span><\/span><\/span><\/span> \u3002\u5b50\u4e32\u5fc5\u987b\u540c\u65f6\u4ee5\u5b57\u6bcd\u5f00\u5934\u548c\u7ed3\u5c3e&#xff0c;\u4e14\u957f\u5ea6\u4ee5\u5176\u5728\u539f\u6587\u672c\u4e2d\u7684\u5b9e\u9645\u5b57\u7b26\u6570&#xff08;\u5305\u62ec\u975e\u5b57\u6bcd&#xff09;\u4e3a\u51c6\u3002<\/p>\n<p>\u76f4\u63a5\u679a\u4e3e\u6240\u6709\u5b50\u4e32\u5e76\u5224\u65ad&#xff0c;\u9700\u8981 <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">O(n3)O(n^3)<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 1.0641em;vertical-align: -0.25em\"><\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0278em\">O<\/span><span class=\"mopen\">(<\/span><span class=\"mord\"><span class=\"mord mathnormal\">n<\/span><span class=\"msupsub\"><span class=\"vlist-t\"><span class=\"vlist-r\"><span class=\"vlist\" style=\"height: 0.8141em\"><span class=\"\" style=\"top: -3.063em;margin-right: 0.05em\"><span class=\"pstrut\" style=\"height: 2.7em\"><\/span><span class=\"sizing reset-size6 size3 mtight\"><span class=\"mord mtight\">3<\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span><span class=\"mclose\">)<\/span><\/span><\/span><\/span><\/span> \u6216 <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">O(n2\u22c5L)O(n^2 \\\\cdot L)<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 1.0641em;vertical-align: -0.25em\"><\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0278em\">O<\/span><span class=\"mopen\">(<\/span><span class=\"mord\"><span class=\"mord mathnormal\">n<\/span><span class=\"msupsub\"><span class=\"vlist-t\"><span class=\"vlist-r\"><span class=\"vlist\" style=\"height: 0.8141em\"><span class=\"\" style=\"top: -3.063em;margin-right: 0.05em\"><span class=\"pstrut\" style=\"height: 2.7em\"><\/span><span class=\"sizing reset-size6 size3 mtight\"><span class=\"mord mtight\">2<\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span><span class=\"mspace\" style=\"margin-right: 0.2222em\"><\/span><span class=\"mbin\">\u22c5<\/span><span class=\"mspace\" style=\"margin-right: 0.2222em\"><\/span><\/span><span class=\"base\"><span class=\"strut\" style=\"height: 1em;vertical-align: -0.25em\"><\/span><span class=\"mord mathnormal\">L<\/span><span class=\"mclose\">)<\/span><\/span><\/span><\/span><\/span> \u7684\u65f6\u95f4&#xff0c;\u5176\u4e2d <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">nn<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.4306em\"><\/span><span class=\"mord mathnormal\">n<\/span><\/span><\/span><\/span><\/span> \u4e3a\u539f\u4e32\u957f\u5ea6&#xff08;<span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">\u22641000\\\\le 1000<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.7719em;vertical-align: -0.136em\"><\/span><span class=\"mrel\">\u2264<\/span><span class=\"mspace\" style=\"margin-right: 0.2778em\"><\/span><\/span><span class=\"base\"><span class=\"strut\" style=\"height: 0.6444em\"><\/span><span class=\"mord\">1000<\/span><\/span><\/span><\/span><\/span>&#xff09;&#xff0c;\u867d\u7136 <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">nn<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.4306em\"><\/span><span class=\"mord mathnormal\">n<\/span><\/span><\/span><\/span><\/span> \u4e0d\u5927&#xff0c;\u4f46 <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">O(n3)O(n^3)<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 1.0641em;vertical-align: -0.25em\"><\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0278em\">O<\/span><span class=\"mopen\">(<\/span><span class=\"mord\"><span class=\"mord mathnormal\">n<\/span><span class=\"msupsub\"><span class=\"vlist-t\"><span class=\"vlist-r\"><span class=\"vlist\" style=\"height: 0.8141em\"><span class=\"\" style=\"top: -3.063em;margin-right: 0.05em\"><span class=\"pstrut\" style=\"height: 2.7em\"><\/span><span class=\"sizing reset-size6 size3 mtight\"><span class=\"mord mtight\">3<\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span><span class=\"mclose\">)<\/span><\/span><\/span><\/span><\/span> \u53ef\u80fd\u8d85\u65f6&#xff08;\u6700\u574f <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">10910^9<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.8141em\"><\/span><span class=\"mord\">1<\/span><span class=\"mord\"><span class=\"mord\">0<\/span><span class=\"msupsub\"><span class=\"vlist-t\"><span class=\"vlist-r\"><span class=\"vlist\" style=\"height: 0.8141em\"><span class=\"\" style=\"top: -3.063em;margin-right: 0.05em\"><span class=\"pstrut\" style=\"height: 2.7em\"><\/span><span class=\"sizing reset-size6 size3 mtight\"><span class=\"mord mtight\">9<\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span> \u91cf\u7ea7&#xff09;\u3002\u6211\u4eec\u9700\u8981\u66f4\u9ad8\u6548\u7684\u65b9\u6cd5\u3002<\/p>\n<p>\u89c2\u5bdf\u56de\u6587\u5224\u65ad\u7684\u672c\u8d28&#xff1a;\u53ea\u5173\u5fc3\u5b57\u6bcd\u5e8f\u5217\u7684\u5bf9\u79f0\u6027\u3002\u56e0\u6b64&#xff0c;\u53ef\u4ee5\u5148\u628a\u6240\u6709\u5b57\u6bcd\u63d0\u53d6\u51fa\u6765&#xff0c;\u8bb0\u5f55\u6bcf\u4e2a\u5b57\u6bcd\u5728\u539f\u4e32\u4e2d\u7684\u4f4d\u7f6e\u3002\u7136\u540e\u95ee\u9898\u8f6c\u5316\u4e3a&#xff1a;\u5728\u5b57\u6bcd\u5e8f\u5217\u4e2d\u627e\u5230\u8fde\u7eed\u533a\u95f4 <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">[l,r][l, r]<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 1em;vertical-align: -0.25em\"><\/span><span class=\"mopen\">[<\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0197em\">l<\/span><span class=\"mpunct\">,<\/span><span class=\"mspace\" style=\"margin-right: 0.1667em\"><\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0278em\">r<\/span><span class=\"mclose\">]<\/span><\/span><\/span><\/span><\/span> &#xff0c;\u4f7f\u5f97\u8be5\u533a\u95f4\u4e0e\u5176\u53cd\u8f6c\u7684\u5bf9\u5e94\u4f4d\u7f6e\u4e0d\u540c\u7684\u4e2a\u6570 <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">diff(l,r)\u22642k\\\\textit{diff}(l, r) \\\\le 2k<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 1em;vertical-align: -0.25em\"><\/span><span class=\"mord text\"><span class=\"mord textit\">diff<\/span><\/span><span class=\"mopen\">(<\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0197em\">l<\/span><span class=\"mpunct\">,<\/span><span class=\"mspace\" style=\"margin-right: 0.1667em\"><\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0278em\">r<\/span><span class=\"mclose\">)<\/span><span class=\"mspace\" style=\"margin-right: 0.2778em\"><\/span><span class=\"mrel\">\u2264<\/span><span class=\"mspace\" style=\"margin-right: 0.2778em\"><\/span><\/span><span class=\"base\"><span class=\"strut\" style=\"height: 0.6944em\"><\/span><span class=\"mord\">2<\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0315em\">k<\/span><\/span><\/span><\/span><\/span> &#xff0c;\u7136\u540e\u8ba1\u7b97\u5176\u5bf9\u5e94\u7684\u539f\u59cb\u957f\u5ea6 <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">pos[r]\u2212pos[l]&#043;1\\\\textit{pos}[r] &#8211; \\\\textit{pos}[l] &#043; 1<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 1em;vertical-align: -0.25em\"><\/span><span class=\"mord text\"><span class=\"mord textit\">pos<\/span><\/span><span class=\"mopen\">[<\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0278em\">r<\/span><span class=\"mclose\">]<\/span><span class=\"mspace\" style=\"margin-right: 0.2222em\"><\/span><span class=\"mbin\">\u2212<\/span><span class=\"mspace\" style=\"margin-right: 0.2222em\"><\/span><\/span><span class=\"base\"><span class=\"strut\" style=\"height: 1em;vertical-align: -0.25em\"><\/span><span class=\"mord text\"><span class=\"mord textit\">pos<\/span><\/span><span class=\"mopen\">[<\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0197em\">l<\/span><span class=\"mclose\">]<\/span><span class=\"mspace\" style=\"margin-right: 0.2222em\"><\/span><span class=\"mbin\">&#043;<\/span><span class=\"mspace\" style=\"margin-right: 0.2222em\"><\/span><\/span><span class=\"base\"><span class=\"strut\" style=\"height: 0.6444em\"><\/span><span class=\"mord\">1<\/span><\/span><\/span><\/span><\/span> &#xff0c;\u5e76\u8bb0\u5f55\u6700\u5927\u7684\u539f\u59cb\u957f\u5ea6\u548c\u6700\u5c0f\u7684\u8d77\u59cb\u4f4d\u7f6e\u3002<\/p>\n<h3>\u89e3\u9898\u601d\u8def<\/h3>\n<h4>\u63d0\u53d6\u5b57\u6bcd\u4e0e\u4f4d\u7f6e\u6620\u5c04<\/h4>\n<p>\u904d\u5386\u539f\u5b57\u7b26\u4e32&#xff0c;\u6bcf\u5f53\u9047\u5230\u5b57\u6bcd\u65f6&#xff0c;\u5c06\u5176\u8f6c\u6362\u4e3a\u5c0f\u5199&#xff0c;\u5b58\u5165\u6570\u7ec4 <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">letters\\\\textit{letters}<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.6944em\"><\/span><span class=\"mord text\"><span class=\"mord textit\">letters<\/span><\/span><\/span><\/span><\/span><\/span> &#xff0c;\u540c\u65f6\u5c06\u8be5\u5b57\u7b26\u5728\u539f\u4e32\u4e2d\u7684\u4e0b\u6807&#xff08;<span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">00<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.6444em\"><\/span><span class=\"mord\">0<\/span><\/span><\/span><\/span><\/span>\u2011based&#xff09;\u5b58\u5165\u6570\u7ec4 <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">pos\\\\textit{pos}<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.625em;vertical-align: -0.1944em\"><\/span><span class=\"mord text\"><span class=\"mord textit\">pos<\/span><\/span><\/span><\/span><\/span><\/span> \u3002\u8fd9\u6837&#xff0c;\u539f\u4e32\u7684\u4efb\u610f\u5b50\u4e32\u82e5\u9996\u5c3e\u90fd\u662f\u5b57\u6bcd&#xff0c;\u5219\u5bf9\u5e94\u4e8e <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">letters\\\\textit{letters}<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.6944em\"><\/span><span class=\"mord text\"><span class=\"mord textit\">letters<\/span><\/span><\/span><\/span><\/span><\/span> \u4e2d\u7684\u4e00\u6bb5\u8fde\u7eed\u533a\u95f4 <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">[l,r][l, r]<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 1em;vertical-align: -0.25em\"><\/span><span class=\"mopen\">[<\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0197em\">l<\/span><span class=\"mpunct\">,<\/span><span class=\"mspace\" style=\"margin-right: 0.1667em\"><\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0278em\">r<\/span><span class=\"mclose\">]<\/span><\/span><\/span><\/span><\/span> &#xff0c;\u5176\u539f\u59cb\u957f\u5ea6\u4e3a <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">pos[r]\u2212pos[l]&#043;1\\\\textit{pos}[r] &#8211; \\\\textit{pos}[l] &#043; 1<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 1em;vertical-align: -0.25em\"><\/span><span class=\"mord text\"><span class=\"mord textit\">pos<\/span><\/span><span class=\"mopen\">[<\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0278em\">r<\/span><span class=\"mclose\">]<\/span><span class=\"mspace\" style=\"margin-right: 0.2222em\"><\/span><span class=\"mbin\">\u2212<\/span><span class=\"mspace\" style=\"margin-right: 0.2222em\"><\/span><\/span><span class=\"base\"><span class=\"strut\" style=\"height: 1em;vertical-align: -0.25em\"><\/span><span class=\"mord text\"><span class=\"mord textit\">pos<\/span><\/span><span class=\"mopen\">[<\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0197em\">l<\/span><span class=\"mclose\">]<\/span><span class=\"mspace\" style=\"margin-right: 0.2222em\"><\/span><span class=\"mbin\">&#043;<\/span><span class=\"mspace\" style=\"margin-right: 0.2222em\"><\/span><\/span><span class=\"base\"><span class=\"strut\" style=\"height: 0.6444em\"><\/span><span class=\"mord\">1<\/span><\/span><\/span><\/span><\/span> &#xff0c;\u8d77\u59cb\u4f4d\u7f6e\u4e3a <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">pos[l]&#043;1\\\\textit{pos}[l] &#043; 1<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 1em;vertical-align: -0.25em\"><\/span><span class=\"mord text\"><span class=\"mord textit\">pos<\/span><\/span><span class=\"mopen\">[<\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0197em\">l<\/span><span class=\"mclose\">]<\/span><span class=\"mspace\" style=\"margin-right: 0.2222em\"><\/span><span class=\"mbin\">&#043;<\/span><span class=\"mspace\" style=\"margin-right: 0.2222em\"><\/span><\/span><span class=\"base\"><span class=\"strut\" style=\"height: 0.6444em\"><\/span><span class=\"mord\">1<\/span><\/span><\/span><\/span><\/span> \u3002<\/p>\n<h4>\u8ba1\u7b97\u533a\u95f4\u5dee\u5f02\u6570<\/h4>\n<p>\u6211\u4eec\u9700\u8981\u5feb\u901f\u5f97\u5230\u4efb\u610f\u533a\u95f4 <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">[l,r][l, r]<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 1em;vertical-align: -0.25em\"><\/span><span class=\"mopen\">[<\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0197em\">l<\/span><span class=\"mpunct\">,<\/span><span class=\"mspace\" style=\"margin-right: 0.1667em\"><\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0278em\">r<\/span><span class=\"mclose\">]<\/span><\/span><\/span><\/span><\/span> \u7684\u5dee\u5f02\u6570 <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">diff(l,r)\\\\textit{diff}(l, r)<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 1em;vertical-align: -0.25em\"><\/span><span class=\"mord text\"><span class=\"mord textit\">diff<\/span><\/span><span class=\"mopen\">(<\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0197em\">l<\/span><span class=\"mpunct\">,<\/span><span class=\"mspace\" style=\"margin-right: 0.1667em\"><\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0278em\">r<\/span><span class=\"mclose\">)<\/span><\/span><\/span><\/span><\/span> &#xff0c;\u5b9a\u4e49\u4e3a\u533a\u95f4\u5185\u5bf9\u79f0\u4f4d\u7f6e&#xff08;<span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">ii<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.6595em\"><\/span><span class=\"mord mathnormal\">i<\/span><\/span><\/span><\/span><\/span> \u4e0e <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">r\u2212(i\u2212l)r &#8211; (i-l)<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.6667em;vertical-align: -0.0833em\"><\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0278em\">r<\/span><span class=\"mspace\" style=\"margin-right: 0.2222em\"><\/span><span class=\"mbin\">\u2212<\/span><span class=\"mspace\" style=\"margin-right: 0.2222em\"><\/span><\/span><span class=\"base\"><span class=\"strut\" style=\"height: 1em;vertical-align: -0.25em\"><\/span><span class=\"mopen\">(<\/span><span class=\"mord mathnormal\">i<\/span><span class=\"mspace\" style=\"margin-right: 0.2222em\"><\/span><span class=\"mbin\">\u2212<\/span><span class=\"mspace\" style=\"margin-right: 0.2222em\"><\/span><\/span><span class=\"base\"><span class=\"strut\" style=\"height: 1em;vertical-align: -0.25em\"><\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0197em\">l<\/span><span class=\"mclose\">)<\/span><\/span><\/span><\/span><\/span> &#xff09;\u5b57\u7b26\u4e0d\u540c\u7684\u4e2a\u6570&#xff08;\u6bcf\u4e2a\u4e0d\u540c\u4f4d\u7f6e\u8d21\u732e <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">11<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.6444em\"><\/span><span class=\"mord\">1<\/span><\/span><\/span><\/span><\/span> &#xff0c;\u6ce8\u610f\u5bf9\u79f0\u7684\u4e24\u4e2a\u4f4d\u7f6e\u5404\u7b97\u4e00\u4e2a&#xff0c;\u6545\u82e5 <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">letters[l&#043;i]\u2260letters[r\u2212i]\\\\textit{letters}[l&#043;i] \\\\ne \\\\textit{letters}[r-i]<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 1em;vertical-align: -0.25em\"><\/span><span class=\"mord text\"><span class=\"mord textit\">letters<\/span><\/span><span class=\"mopen\">[<\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0197em\">l<\/span><span class=\"mspace\" style=\"margin-right: 0.2222em\"><\/span><span class=\"mbin\">&#043;<\/span><span class=\"mspace\" style=\"margin-right: 0.2222em\"><\/span><\/span><span class=\"base\"><span class=\"strut\" style=\"height: 1em;vertical-align: -0.25em\"><\/span><span class=\"mord mathnormal\">i<\/span><span class=\"mclose\">]<\/span><span class=\"mspace\" style=\"margin-right: 0.2778em\"><\/span><span class=\"mrel\"><span class=\"mrel\"><span class=\"mord vbox\"><span class=\"thinbox\"><span class=\"rlap\"><span class=\"strut\" style=\"height: 0.8889em;vertical-align: -0.1944em\"><\/span><span class=\"inner\"><span class=\"mord\"><span class=\"mrel\">\ue020<\/span><\/span><\/span><span class=\"fix\"><\/span><\/span><\/span><\/span><\/span><span class=\"mspace nobreak\"><\/span><span class=\"mrel\">&#061;<\/span><\/span><span class=\"mspace\" style=\"margin-right: 0.2778em\"><\/span><\/span><span class=\"base\"><span class=\"strut\" style=\"height: 1em;vertical-align: -0.25em\"><\/span><span class=\"mord text\"><span class=\"mord textit\">letters<\/span><\/span><span class=\"mopen\">[<\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0278em\">r<\/span><span class=\"mspace\" style=\"margin-right: 0.2222em\"><\/span><span class=\"mbin\">\u2212<\/span><span class=\"mspace\" style=\"margin-right: 0.2222em\"><\/span><\/span><span class=\"base\"><span class=\"strut\" style=\"height: 1em;vertical-align: -0.25em\"><\/span><span class=\"mord mathnormal\">i<\/span><span class=\"mclose\">]<\/span><\/span><\/span><\/span><\/span> &#xff0c;\u5219\u8fd9\u4e24\u4e2a\u4f4d\u7f6e\u90fd\u4e0d\u540c&#xff0c;\u8d21\u732e <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">22<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.6444em\"><\/span><span class=\"mord\">2<\/span><\/span><\/span><\/span><\/span> &#xff09;\u3002<\/p>\n<p>\u6211\u4eec\u4f7f\u7528\u52a8\u6001\u89c4\u5212\u9884\u5904\u7406\u6240\u6709\u533a\u95f4\u7684\u5dee\u5f02\u6570\u3002\u8bbe <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">dp[l][r]\\\\textit{dp}[l][r]<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 1em;vertical-align: -0.25em\"><\/span><span class=\"mord text\"><span class=\"mord textit\">dp<\/span><\/span><span class=\"mopen\">[<\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0197em\">l<\/span><span class=\"mclose\">]<\/span><span class=\"mopen\">[<\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0278em\">r<\/span><span class=\"mclose\">]<\/span><\/span><\/span><\/span><\/span> \u8868\u793a\u533a\u95f4 <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">[l,r][l, r]<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 1em;vertical-align: -0.25em\"><\/span><span class=\"mopen\">[<\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0197em\">l<\/span><span class=\"mpunct\">,<\/span><span class=\"mspace\" style=\"margin-right: 0.1667em\"><\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0278em\">r<\/span><span class=\"mclose\">]<\/span><\/span><\/span><\/span><\/span> \u4e0e\u5176\u53cd\u8f6c\u7684\u5dee\u5f02\u4f4d\u7f6e\u603b\u6570\u3002\u8f6c\u79fb\u5173\u7cfb\u5982\u4e0b&#xff1a;<\/p>\n<ul>\n<li>\u5f53\u533a\u95f4\u957f\u5ea6 <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">len&#061;1len &#061; 1<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.6944em\"><\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0197em\">l<\/span><span class=\"mord mathnormal\">e<\/span><span class=\"mord mathnormal\">n<\/span><span class=\"mspace\" style=\"margin-right: 0.2778em\"><\/span><span class=\"mrel\">&#061;<\/span><span class=\"mspace\" style=\"margin-right: 0.2778em\"><\/span><\/span><span class=\"base\"><span class=\"strut\" style=\"height: 0.6444em\"><\/span><span class=\"mord\">1<\/span><\/span><\/span><\/span><\/span> \u65f6&#xff0c;<span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">dp[l][l]&#061;0\\\\textit{dp}[l][l] &#061; 0<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 1em;vertical-align: -0.25em\"><\/span><span class=\"mord text\"><span class=\"mord textit\">dp<\/span><\/span><span class=\"mopen\">[<\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0197em\">l<\/span><span class=\"mclose\">]<\/span><span class=\"mopen\">[<\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0197em\">l<\/span><span class=\"mclose\">]<\/span><span class=\"mspace\" style=\"margin-right: 0.2778em\"><\/span><span class=\"mrel\">&#061;<\/span><span class=\"mspace\" style=\"margin-right: 0.2778em\"><\/span><\/span><span class=\"base\"><span class=\"strut\" style=\"height: 0.6444em\"><\/span><span class=\"mord\">0<\/span><\/span><\/span><\/span><\/span> &#xff1b;<\/li>\n<li>\u5f53 <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">len\u22652len \\\\ge 2<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.8304em;vertical-align: -0.136em\"><\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0197em\">l<\/span><span class=\"mord mathnormal\">e<\/span><span class=\"mord mathnormal\">n<\/span><span class=\"mspace\" style=\"margin-right: 0.2778em\"><\/span><span class=\"mrel\">\u2265<\/span><span class=\"mspace\" style=\"margin-right: 0.2778em\"><\/span><\/span><span class=\"base\"><span class=\"strut\" style=\"height: 0.6444em\"><\/span><span class=\"mord\">2<\/span><\/span><\/span><\/span><\/span> \u65f6&#xff0c;<span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">dp[l][r]&#061;dp[l&#043;1][r\u22121]&#043;(letters[l]\u2260letters[r])\u00d72\\\\textit{dp}[l][r] &#061; \\\\textit{dp}[l&#043;1][r-1] &#043; \\\\big( \\\\textit{letters}[l] \\\\ne \\\\textit{letters}[r] \\\\big) \\\\times 2<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 1em;vertical-align: -0.25em\"><\/span><span class=\"mord text\"><span class=\"mord textit\">dp<\/span><\/span><span class=\"mopen\">[<\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0197em\">l<\/span><span class=\"mclose\">]<\/span><span class=\"mopen\">[<\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0278em\">r<\/span><span class=\"mclose\">]<\/span><span class=\"mspace\" style=\"margin-right: 0.2778em\"><\/span><span class=\"mrel\">&#061;<\/span><span class=\"mspace\" style=\"margin-right: 0.2778em\"><\/span><\/span><span class=\"base\"><span class=\"strut\" style=\"height: 1em;vertical-align: -0.25em\"><\/span><span class=\"mord text\"><span class=\"mord textit\">dp<\/span><\/span><span class=\"mopen\">[<\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0197em\">l<\/span><span class=\"mspace\" style=\"margin-right: 0.2222em\"><\/span><span class=\"mbin\">&#043;<\/span><span class=\"mspace\" style=\"margin-right: 0.2222em\"><\/span><\/span><span class=\"base\"><span class=\"strut\" style=\"height: 1em;vertical-align: -0.25em\"><\/span><span class=\"mord\">1<\/span><span class=\"mclose\">]<\/span><span class=\"mopen\">[<\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0278em\">r<\/span><span class=\"mspace\" style=\"margin-right: 0.2222em\"><\/span><span class=\"mbin\">\u2212<\/span><span class=\"mspace\" style=\"margin-right: 0.2222em\"><\/span><\/span><span class=\"base\"><span class=\"strut\" style=\"height: 1em;vertical-align: -0.25em\"><\/span><span class=\"mord\">1<\/span><span class=\"mclose\">]<\/span><span class=\"mspace\" style=\"margin-right: 0.2222em\"><\/span><span class=\"mbin\">&#043;<\/span><span class=\"mspace\" style=\"margin-right: 0.2222em\"><\/span><\/span><span class=\"base\"><span class=\"strut\" style=\"height: 1.2em;vertical-align: -0.35em\"><\/span><span class=\"mord\"><span class=\"delimsizing size1\">(<\/span><\/span><span class=\"mord text\"><span class=\"mord textit\">letters<\/span><\/span><span class=\"mopen\">[<\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0197em\">l<\/span><span class=\"mclose\">]<\/span><span class=\"mspace\" style=\"margin-right: 0.2778em\"><\/span><span class=\"mrel\"><span class=\"mrel\"><span class=\"mord vbox\"><span class=\"thinbox\"><span class=\"rlap\"><span class=\"strut\" style=\"height: 0.8889em;vertical-align: -0.1944em\"><\/span><span class=\"inner\"><span class=\"mord\"><span class=\"mrel\">\ue020<\/span><\/span><\/span><span class=\"fix\"><\/span><\/span><\/span><\/span><\/span><span class=\"mspace nobreak\"><\/span><span class=\"mrel\">&#061;<\/span><\/span><span class=\"mspace\" style=\"margin-right: 0.2778em\"><\/span><\/span><span class=\"base\"><span class=\"strut\" style=\"height: 1.2em;vertical-align: -0.35em\"><\/span><span class=\"mord text\"><span class=\"mord textit\">letters<\/span><\/span><span class=\"mopen\">[<\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0278em\">r<\/span><span class=\"mclose\">]<\/span><span class=\"mord\"><span class=\"delimsizing size1\">)<\/span><\/span><span class=\"mspace\" style=\"margin-right: 0.2222em\"><\/span><span class=\"mbin\">\u00d7<\/span><span class=\"mspace\" style=\"margin-right: 0.2222em\"><\/span><\/span><span class=\"base\"><span class=\"strut\" style=\"height: 0.6444em\"><\/span><span class=\"mord\">2<\/span><\/span><\/span><\/span><\/span> &#xff0c;\u5176\u4e2d\u5f53 <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">len&#061;2len &#061; 2<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.6944em\"><\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0197em\">l<\/span><span class=\"mord mathnormal\">e<\/span><span class=\"mord mathnormal\">n<\/span><span class=\"mspace\" style=\"margin-right: 0.2778em\"><\/span><span class=\"mrel\">&#061;<\/span><span class=\"mspace\" style=\"margin-right: 0.2778em\"><\/span><\/span><span class=\"base\"><span class=\"strut\" style=\"height: 0.6444em\"><\/span><span class=\"mord\">2<\/span><\/span><\/span><\/span><\/span> \u65f6&#xff0c;<span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">dp[l&#043;1][r\u22121]\\\\textit{dp}[l&#043;1][r-1]<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 1em;vertical-align: -0.25em\"><\/span><span class=\"mord text\"><span class=\"mord textit\">dp<\/span><\/span><span class=\"mopen\">[<\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0197em\">l<\/span><span class=\"mspace\" style=\"margin-right: 0.2222em\"><\/span><span class=\"mbin\">&#043;<\/span><span class=\"mspace\" style=\"margin-right: 0.2222em\"><\/span><\/span><span class=\"base\"><span class=\"strut\" style=\"height: 1em;vertical-align: -0.25em\"><\/span><span class=\"mord\">1<\/span><span class=\"mclose\">]<\/span><span class=\"mopen\">[<\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0278em\">r<\/span><span class=\"mspace\" style=\"margin-right: 0.2222em\"><\/span><span class=\"mbin\">\u2212<\/span><span class=\"mspace\" style=\"margin-right: 0.2222em\"><\/span><\/span><span class=\"base\"><span class=\"strut\" style=\"height: 1em;vertical-align: -0.25em\"><\/span><span class=\"mord\">1<\/span><span class=\"mclose\">]<\/span><\/span><\/span><\/span><\/span> \u89c6\u4e3a <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">00<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.6444em\"><\/span><span class=\"mord\">0<\/span><\/span><\/span><\/span><\/span> \u3002<\/li>\n<\/ul>\n<p>\u6309\u533a\u95f4\u957f\u5ea6\u4ece\u5c0f\u5230\u5927\u8ba1\u7b97\u5373\u53ef\u3002\u7531\u4e8e\u5b57\u6bcd\u4e2a\u6570 <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">mm<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.4306em\"><\/span><span class=\"mord mathnormal\">m<\/span><\/span><\/span><\/span><\/span> \u4e0d\u8d85\u8fc7 <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">10001000<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.6444em\"><\/span><span class=\"mord\">1000<\/span><\/span><\/span><\/span><\/span> &#xff0c;\u4e8c\u7ef4\u6570\u7ec4\u5927\u5c0f\u4e3a <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">m\u00d7mm \\\\times m<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.6667em;vertical-align: -0.0833em\"><\/span><span class=\"mord mathnormal\">m<\/span><span class=\"mspace\" style=\"margin-right: 0.2222em\"><\/span><span class=\"mbin\">\u00d7<\/span><span class=\"mspace\" style=\"margin-right: 0.2222em\"><\/span><\/span><span class=\"base\"><span class=\"strut\" style=\"height: 0.4306em\"><\/span><span class=\"mord mathnormal\">m<\/span><\/span><\/span><\/span><\/span> &#xff0c;\u65f6\u95f4\u548c\u7a7a\u95f4\u5747\u53ef\u884c\u3002<\/p>\n<h4>\u679a\u4e3e\u6240\u6709\u5408\u6cd5\u533a\u95f4<\/h4>\n<p>\u5bf9\u4e8e\u6bcf\u4e00\u5bf9 <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">0\u2264l\u2264r&lt;m0 \\\\le l \\\\le r &lt; m<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.7804em;vertical-align: -0.136em\"><\/span><span class=\"mord\">0<\/span><span class=\"mspace\" style=\"margin-right: 0.2778em\"><\/span><span class=\"mrel\">\u2264<\/span><span class=\"mspace\" style=\"margin-right: 0.2778em\"><\/span><\/span><span class=\"base\"><span class=\"strut\" style=\"height: 0.8304em;vertical-align: -0.136em\"><\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0197em\">l<\/span><span class=\"mspace\" style=\"margin-right: 0.2778em\"><\/span><span class=\"mrel\">\u2264<\/span><span class=\"mspace\" style=\"margin-right: 0.2778em\"><\/span><\/span><span class=\"base\"><span class=\"strut\" style=\"height: 0.5782em;vertical-align: -0.0391em\"><\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0278em\">r<\/span><span class=\"mspace\" style=\"margin-right: 0.2778em\"><\/span><span class=\"mrel\">&lt;<\/span><span class=\"mspace\" style=\"margin-right: 0.2778em\"><\/span><\/span><span class=\"base\"><span class=\"strut\" style=\"height: 0.4306em\"><\/span><span class=\"mord mathnormal\">m<\/span><\/span><\/span><\/span><\/span> &#xff0c;\u82e5 <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">dp[l][r]\u22642k\\\\textit{dp}[l][r] \\\\le 2k<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 1em;vertical-align: -0.25em\"><\/span><span class=\"mord text\"><span class=\"mord textit\">dp<\/span><\/span><span class=\"mopen\">[<\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0197em\">l<\/span><span class=\"mclose\">]<\/span><span class=\"mopen\">[<\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0278em\">r<\/span><span class=\"mclose\">]<\/span><span class=\"mspace\" style=\"margin-right: 0.2778em\"><\/span><span class=\"mrel\">\u2264<\/span><span class=\"mspace\" style=\"margin-right: 0.2778em\"><\/span><\/span><span class=\"base\"><span class=\"strut\" style=\"height: 0.6944em\"><\/span><span class=\"mord\">2<\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0315em\">k<\/span><\/span><\/span><\/span><\/span> &#xff0c;\u5219\u8be5\u533a\u95f4\u5bf9\u5e94\u7684\u539f\u4e32\u5b50\u4e32\u662f\u4e00\u4e2a\u5408\u6cd5\u5019\u9009\u3002\u8ba1\u7b97\u5176\u539f\u59cb\u957f\u5ea6 <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">curLen&#061;pos[r]\u2212pos[l]&#043;1\\\\textit{curLen} &#061; \\\\textit{pos}[r] &#8211; \\\\textit{pos}[l] &#043; 1<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.6833em\"><\/span><span class=\"mord text\"><span class=\"mord textit\">curLen<\/span><\/span><span class=\"mspace\" style=\"margin-right: 0.2778em\"><\/span><span class=\"mrel\">&#061;<\/span><span class=\"mspace\" style=\"margin-right: 0.2778em\"><\/span><\/span><span class=\"base\"><span class=\"strut\" style=\"height: 1em;vertical-align: -0.25em\"><\/span><span class=\"mord text\"><span class=\"mord textit\">pos<\/span><\/span><span class=\"mopen\">[<\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0278em\">r<\/span><span class=\"mclose\">]<\/span><span class=\"mspace\" style=\"margin-right: 0.2222em\"><\/span><span class=\"mbin\">\u2212<\/span><span class=\"mspace\" style=\"margin-right: 0.2222em\"><\/span><\/span><span class=\"base\"><span class=\"strut\" style=\"height: 1em;vertical-align: -0.25em\"><\/span><span class=\"mord text\"><span class=\"mord textit\">pos<\/span><\/span><span class=\"mopen\">[<\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0197em\">l<\/span><span class=\"mclose\">]<\/span><span class=\"mspace\" style=\"margin-right: 0.2222em\"><\/span><span class=\"mbin\">&#043;<\/span><span class=\"mspace\" style=\"margin-right: 0.2222em\"><\/span><\/span><span class=\"base\"><span class=\"strut\" style=\"height: 0.6444em\"><\/span><span class=\"mord\">1<\/span><\/span><\/span><\/span><\/span> \u548c\u8d77\u59cb\u4f4d\u7f6e <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">curStart&#061;pos[l]&#043;1\\\\textit{curStart} &#061; \\\\textit{pos}[l] &#043; 1<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.6833em\"><\/span><span class=\"mord text\"><span class=\"mord textit\">curStart<\/span><\/span><span class=\"mspace\" style=\"margin-right: 0.2778em\"><\/span><span class=\"mrel\">&#061;<\/span><span class=\"mspace\" style=\"margin-right: 0.2778em\"><\/span><\/span><span class=\"base\"><span class=\"strut\" style=\"height: 1em;vertical-align: -0.25em\"><\/span><span class=\"mord text\"><span class=\"mord textit\">pos<\/span><\/span><span class=\"mopen\">[<\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0197em\">l<\/span><span class=\"mclose\">]<\/span><span class=\"mspace\" style=\"margin-right: 0.2222em\"><\/span><span class=\"mbin\">&#043;<\/span><span class=\"mspace\" style=\"margin-right: 0.2222em\"><\/span><\/span><span class=\"base\"><span class=\"strut\" style=\"height: 0.6444em\"><\/span><span class=\"mord\">1<\/span><\/span><\/span><\/span><\/span> &#xff0c;\u5e76\u66f4\u65b0\u5168\u5c40\u6700\u4f18\u89e3&#xff1a;\u4f18\u5148\u6bd4\u8f83\u957f\u5ea6&#xff0c;\u957f\u5ea6\u76f8\u540c\u65f6\u53d6\u8d77\u59cb\u4f4d\u7f6e\u66f4\u5c0f\u8005\u3002<\/p>\n<p>\u6700\u7ec8\u8f93\u51fa\u6700\u4f18\u957f\u5ea6\u548c\u8d77\u59cb\u4f4d\u7f6e\u3002<\/p>\n<h4>\u590d\u6742\u5ea6\u5206\u6790<\/h4>\n<ul>\n<li>\u63d0\u53d6\u5b57\u6bcd&#xff1a;<span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">O(n)O(n)<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 1em;vertical-align: -0.25em\"><\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0278em\">O<\/span><span class=\"mopen\">(<\/span><span class=\"mord mathnormal\">n<\/span><span class=\"mclose\">)<\/span><\/span><\/span><\/span><\/span> &#xff0c;\u5176\u4e2d <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">nn<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.4306em\"><\/span><span class=\"mord mathnormal\">n<\/span><\/span><\/span><\/span><\/span> \u4e3a\u539f\u4e32\u957f\u5ea6\u3002<\/li>\n<li>DP \u8ba1\u7b97&#xff1a;<span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">O(m2)O(m^2)<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 1.0641em;vertical-align: -0.25em\"><\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0278em\">O<\/span><span class=\"mopen\">(<\/span><span class=\"mord\"><span class=\"mord mathnormal\">m<\/span><span class=\"msupsub\"><span class=\"vlist-t\"><span class=\"vlist-r\"><span class=\"vlist\" style=\"height: 0.8141em\"><span class=\"\" style=\"top: -3.063em;margin-right: 0.05em\"><span class=\"pstrut\" style=\"height: 2.7em\"><\/span><span class=\"sizing reset-size6 size3 mtight\"><span class=\"mord mtight\">2<\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span><span class=\"mclose\">)<\/span><\/span><\/span><\/span><\/span> &#xff0c;<span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">mm<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.4306em\"><\/span><span class=\"mord mathnormal\">m<\/span><\/span><\/span><\/span><\/span> \u4e3a\u5b57\u6bcd\u4e2a\u6570&#xff0c;\u6700\u5927 <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">10001000<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.6444em\"><\/span><span class=\"mord\">1000<\/span><\/span><\/span><\/span><\/span> &#xff0c;\u7ea6 <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">10610^6<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.8141em\"><\/span><span class=\"mord\">1<\/span><span class=\"mord\"><span class=\"mord\">0<\/span><span class=\"msupsub\"><span class=\"vlist-t\"><span class=\"vlist-r\"><span class=\"vlist\" style=\"height: 0.8141em\"><span class=\"\" style=\"top: -3.063em;margin-right: 0.05em\"><span class=\"pstrut\" style=\"height: 2.7em\"><\/span><span class=\"sizing reset-size6 size3 mtight\"><span class=\"mord mtight\">6<\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span> \u6b21\u64cd\u4f5c\u3002<\/li>\n<li>\u679a\u4e3e\u533a\u95f4&#xff1a;<span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">O(m2)O(m^2)<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 1.0641em;vertical-align: -0.25em\"><\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0278em\">O<\/span><span class=\"mopen\">(<\/span><span class=\"mord\"><span class=\"mord mathnormal\">m<\/span><span class=\"msupsub\"><span class=\"vlist-t\"><span class=\"vlist-r\"><span class=\"vlist\" style=\"height: 0.8141em\"><span class=\"\" style=\"top: -3.063em;margin-right: 0.05em\"><span class=\"pstrut\" style=\"height: 2.7em\"><\/span><span class=\"sizing reset-size6 size3 mtight\"><span class=\"mord mtight\">2<\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span><span class=\"mclose\">)<\/span><\/span><\/span><\/span><\/span> \u3002<\/li>\n<li>\u603b\u65f6\u95f4\u590d\u6742\u5ea6&#xff1a;<span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">O(n&#043;m2)O(n &#043; m^2)<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 1em;vertical-align: -0.25em\"><\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0278em\">O<\/span><span class=\"mopen\">(<\/span><span class=\"mord mathnormal\">n<\/span><span class=\"mspace\" style=\"margin-right: 0.2222em\"><\/span><span class=\"mbin\">&#043;<\/span><span class=\"mspace\" style=\"margin-right: 0.2222em\"><\/span><\/span><span class=\"base\"><span class=\"strut\" style=\"height: 1.0641em;vertical-align: -0.25em\"><\/span><span class=\"mord\"><span class=\"mord mathnormal\">m<\/span><span class=\"msupsub\"><span class=\"vlist-t\"><span class=\"vlist-r\"><span class=\"vlist\" style=\"height: 0.8141em\"><span class=\"\" style=\"top: -3.063em;margin-right: 0.05em\"><span class=\"pstrut\" style=\"height: 2.7em\"><\/span><span class=\"sizing reset-size6 size3 mtight\"><span class=\"mord mtight\">2<\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span><span class=\"mclose\">)<\/span><\/span><\/span><\/span><\/span> &#xff0c;\u7a7a\u95f4\u590d\u6742\u5ea6&#xff1a;<span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">O(m2)O(m^2)<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 1.0641em;vertical-align: -0.25em\"><\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0278em\">O<\/span><span class=\"mopen\">(<\/span><span class=\"mord\"><span class=\"mord mathnormal\">m<\/span><span class=\"msupsub\"><span class=\"vlist-t\"><span class=\"vlist-r\"><span class=\"vlist\" style=\"height: 0.8141em\"><span class=\"\" style=\"top: -3.063em;margin-right: 0.05em\"><span class=\"pstrut\" style=\"height: 2.7em\"><\/span><span class=\"sizing reset-size6 size3 mtight\"><span class=\"mord mtight\">2<\/span><\/span><\/span><\/span><\/span><\/span><\/span><\/span><span class=\"mclose\">)<\/span><\/span><\/span><\/span><\/span> &#xff0c;\u5b8c\u5168\u53ef\u4ee5\u6ee1\u8db3\u9898\u76ee\u9650\u5236&#xff08;\u6700\u591a <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">2525<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.6444em\"><\/span><span class=\"mord\">25<\/span><\/span><\/span><\/span><\/span> \u4e2a\u6d4b\u8bd5\u7528\u4f8b&#xff09;\u3002<\/li>\n<\/ul>\n<h3>\u4ee3\u7801\u5b9e\u73b0<\/h3>\n<p><span class=\"token comment\">\/\/ Almost Palindrome<\/span><br \/>\n<span class=\"token comment\">\/\/ UVa ID: 12656<\/span><br \/>\n<span class=\"token comment\">\/\/ Verdict: Accepted<\/span><br \/>\n<span class=\"token comment\">\/\/ Submission Date: 2026-06-24<\/span><br \/>\n<span class=\"token comment\">\/\/ UVa Run Time: 0.020s<\/span><br \/>\n<span class=\"token comment\">\/\/<\/span><br \/>\n<span class=\"token comment\">\/\/ \u7248\u6743\u6240\u6709&#xff08;C&#xff09;2026&#xff0c;\u90b1\u79cb\u3002metaphysis # yeah dot net<\/span><\/p>\n<p><span class=\"token macro property\"><span class=\"token directive-hash\">#<\/span><span class=\"token directive keyword\">include<\/span> <span class=\"token string\">&lt;bits\/stdc&#043;&#043;.h&gt;<\/span><\/span><br \/>\n<span class=\"token keyword\">using<\/span> <span class=\"token keyword\">namespace<\/span> std<span class=\"token punctuation\">;<\/span><\/p>\n<p><span class=\"token keyword\">int<\/span> <span class=\"token function\">main<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n    ios<span class=\"token double-colon punctuation\">::<\/span><span class=\"token function\">sync_with_stdio<\/span><span class=\"token punctuation\">(<\/span><span class=\"token boolean\">false<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    cin<span class=\"token punctuation\">.<\/span><span class=\"token function\">tie<\/span><span class=\"token punctuation\">(<\/span><span class=\"token keyword\">nullptr<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>    <span class=\"token keyword\">int<\/span> caseNo <span class=\"token operator\">&#061;<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">,<\/span> k<span class=\"token punctuation\">;<\/span><br \/>\n    string line<span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token keyword\">while<\/span> <span class=\"token punctuation\">(<\/span>cin <span class=\"token operator\">&gt;&gt;<\/span> k<span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n        <span class=\"token function\">getline<\/span><span class=\"token punctuation\">(<\/span>cin<span class=\"token punctuation\">,<\/span> line<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span>                     <span class=\"token comment\">\/\/ \u6d88\u8017\u6389 k \u540e\u7684\u6362\u884c\u7b26<\/span><br \/>\n        <span class=\"token function\">getline<\/span><span class=\"token punctuation\">(<\/span>cin<span class=\"token punctuation\">,<\/span> line<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span>                     <span class=\"token comment\">\/\/ \u8bfb\u53d6\u539f\u5b57\u7b26\u4e32&#xff08;\u53ef\u80fd\u542b\u7a7a\u683c&#xff09;<\/span><\/p>\n<p>        vector<span class=\"token operator\">&lt;<\/span><span class=\"token keyword\">char<\/span><span class=\"token operator\">&gt;<\/span> letters<span class=\"token punctuation\">;<\/span>                   <span class=\"token comment\">\/\/ \u5c0f\u5199\u5b57\u6bcd\u5e8f\u5217<\/span><br \/>\n        vector<span class=\"token operator\">&lt;<\/span><span class=\"token keyword\">int<\/span><span class=\"token operator\">&gt;<\/span> pos<span class=\"token punctuation\">;<\/span>                        <span class=\"token comment\">\/\/ \u6bcf\u4e2a\u5b57\u6bcd\u5728\u539f\u4e32\u4e2d\u7684\u4f4d\u7f6e&#xff08;0\u2011based&#xff09;<\/span><br \/>\n        <span class=\"token keyword\">for<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token keyword\">int<\/span> i <span class=\"token operator\">&#061;<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">;<\/span> i <span class=\"token operator\">&lt;<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token keyword\">int<\/span><span class=\"token punctuation\">)<\/span>line<span class=\"token punctuation\">.<\/span><span class=\"token function\">size<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span> <span class=\"token operator\">&#043;&#043;<\/span>i<span class=\"token punctuation\">)<\/span><br \/>\n            <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token function\">isalpha<\/span><span class=\"token punctuation\">(<\/span>line<span class=\"token punctuation\">[<\/span>i<span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n                letters<span class=\"token punctuation\">.<\/span><span class=\"token function\">push_back<\/span><span class=\"token punctuation\">(<\/span><span class=\"token function\">tolower<\/span><span class=\"token punctuation\">(<\/span>line<span class=\"token punctuation\">[<\/span>i<span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n                pos<span class=\"token punctuation\">.<\/span><span class=\"token function\">push_back<\/span><span class=\"token punctuation\">(<\/span>i<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n            <span class=\"token punctuation\">}<\/span><\/p>\n<p>        <span class=\"token keyword\">int<\/span> m <span class=\"token operator\">&#061;<\/span> letters<span class=\"token punctuation\">.<\/span><span class=\"token function\">size<\/span><span class=\"token punctuation\">(<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n        vector<span class=\"token operator\">&lt;<\/span>vector<span class=\"token operator\">&lt;<\/span><span class=\"token keyword\">int<\/span><span class=\"token operator\">&gt;&gt;<\/span> <span class=\"token function\">dp<\/span><span class=\"token punctuation\">(<\/span>m<span class=\"token punctuation\">,<\/span> <span class=\"token generic-function\"><span class=\"token function\">vector<\/span><span class=\"token generic class-name\"><span class=\"token operator\">&lt;<\/span><span class=\"token keyword\">int<\/span><span class=\"token operator\">&gt;<\/span><\/span><\/span><span class=\"token punctuation\">(<\/span>m<span class=\"token punctuation\">,<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><\/p>\n<p>        <span class=\"token comment\">\/\/ \u6309\u957f\u5ea6\u9012\u589e\u8ba1\u7b97 dp[l][r]&#xff08;\u5dee\u5f02\u4f4d\u7f6e\u603b\u6570&#xff09;<\/span><br \/>\n        <span class=\"token keyword\">for<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token keyword\">int<\/span> len <span class=\"token operator\">&#061;<\/span> <span class=\"token number\">1<\/span><span class=\"token punctuation\">;<\/span> len <span class=\"token operator\">&lt;&#061;<\/span> m<span class=\"token punctuation\">;<\/span> <span class=\"token operator\">&#043;&#043;<\/span>len<span class=\"token punctuation\">)<\/span><br \/>\n            <span class=\"token keyword\">for<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token keyword\">int<\/span> l <span class=\"token operator\">&#061;<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">;<\/span> l <span class=\"token operator\">&#043;<\/span> len <span class=\"token operator\">&#8211;<\/span> <span class=\"token number\">1<\/span> <span class=\"token operator\">&lt;<\/span> m<span class=\"token punctuation\">;<\/span> <span class=\"token operator\">&#043;&#043;<\/span>l<span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n                <span class=\"token keyword\">int<\/span> r <span class=\"token operator\">&#061;<\/span> l <span class=\"token operator\">&#043;<\/span> len <span class=\"token operator\">&#8211;<\/span> <span class=\"token number\">1<\/span><span class=\"token punctuation\">;<\/span><br \/>\n                <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>len <span class=\"token operator\">&#061;&#061;<\/span> <span class=\"token number\">1<\/span><span class=\"token punctuation\">)<\/span> dp<span class=\"token punctuation\">[<\/span>l<span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">[<\/span>r<span class=\"token punctuation\">]<\/span> <span class=\"token operator\">&#061;<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">;<\/span><br \/>\n                <span class=\"token keyword\">else<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n                    <span class=\"token keyword\">int<\/span> inner <span class=\"token operator\">&#061;<\/span> <span class=\"token punctuation\">(<\/span>len <span class=\"token operator\">&#061;&#061;<\/span> <span class=\"token number\">2<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token operator\">?<\/span> <span class=\"token number\">0<\/span> <span class=\"token operator\">:<\/span> dp<span class=\"token punctuation\">[<\/span>l <span class=\"token operator\">&#043;<\/span> <span class=\"token number\">1<\/span><span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">[<\/span>r <span class=\"token operator\">&#8211;<\/span> <span class=\"token number\">1<\/span><span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">;<\/span><br \/>\n                    dp<span class=\"token punctuation\">[<\/span>l<span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">[<\/span>r<span class=\"token punctuation\">]<\/span> <span class=\"token operator\">&#061;<\/span> inner <span class=\"token operator\">&#043;<\/span> <span class=\"token punctuation\">(<\/span>letters<span class=\"token punctuation\">[<\/span>l<span class=\"token punctuation\">]<\/span> <span class=\"token operator\">!&#061;<\/span> letters<span class=\"token punctuation\">[<\/span>r<span class=\"token punctuation\">]<\/span> <span class=\"token operator\">?<\/span> <span class=\"token number\">2<\/span> <span class=\"token operator\">:<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">;<\/span><br \/>\n                <span class=\"token punctuation\">}<\/span><br \/>\n            <span class=\"token punctuation\">}<\/span><\/p>\n<p>        <span class=\"token keyword\">int<\/span> bestLen <span class=\"token operator\">&#061;<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">,<\/span> bestStart <span class=\"token operator\">&#061;<\/span> INT_MAX<span class=\"token punctuation\">;<\/span><br \/>\n        <span class=\"token keyword\">int<\/span> limit <span class=\"token operator\">&#061;<\/span> <span class=\"token number\">2<\/span> <span class=\"token operator\">*<\/span> k<span class=\"token punctuation\">;<\/span><br \/>\n        <span class=\"token keyword\">for<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token keyword\">int<\/span> l <span class=\"token operator\">&#061;<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">;<\/span> l <span class=\"token operator\">&lt;<\/span> m<span class=\"token punctuation\">;<\/span> <span class=\"token operator\">&#043;&#043;<\/span>l<span class=\"token punctuation\">)<\/span><br \/>\n            <span class=\"token keyword\">for<\/span> <span class=\"token punctuation\">(<\/span><span class=\"token keyword\">int<\/span> r <span class=\"token operator\">&#061;<\/span> l<span class=\"token punctuation\">;<\/span> r <span class=\"token operator\">&lt;<\/span> m<span class=\"token punctuation\">;<\/span> <span class=\"token operator\">&#043;&#043;<\/span>r<span class=\"token punctuation\">)<\/span><br \/>\n                <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>dp<span class=\"token punctuation\">[<\/span>l<span class=\"token punctuation\">]<\/span><span class=\"token punctuation\">[<\/span>r<span class=\"token punctuation\">]<\/span> <span class=\"token operator\">&lt;&#061;<\/span> limit<span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n                    <span class=\"token keyword\">int<\/span> curLen <span class=\"token operator\">&#061;<\/span> pos<span class=\"token punctuation\">[<\/span>r<span class=\"token punctuation\">]<\/span> <span class=\"token operator\">&#8211;<\/span> pos<span class=\"token punctuation\">[<\/span>l<span class=\"token punctuation\">]<\/span> <span class=\"token operator\">&#043;<\/span> <span class=\"token number\">1<\/span><span class=\"token punctuation\">;<\/span>       <span class=\"token comment\">\/\/ \u539f\u4e32\u4e2d\u8be5\u5b50\u4e32\u7684\u5b9e\u9645\u957f\u5ea6<\/span><br \/>\n                    <span class=\"token keyword\">int<\/span> curStart <span class=\"token operator\">&#061;<\/span> pos<span class=\"token punctuation\">[<\/span>l<span class=\"token punctuation\">]<\/span> <span class=\"token operator\">&#043;<\/span> <span class=\"token number\">1<\/span><span class=\"token punctuation\">;<\/span>              <span class=\"token comment\">\/\/ \u8d77\u59cb\u4f4d\u7f6e&#xff08;1\u2011based&#xff09;<\/span><br \/>\n                    <span class=\"token keyword\">if<\/span> <span class=\"token punctuation\">(<\/span>curLen <span class=\"token operator\">&gt;<\/span> bestLen <span class=\"token operator\">||<\/span> <span class=\"token punctuation\">(<\/span>curLen <span class=\"token operator\">&#061;&#061;<\/span> bestLen <span class=\"token operator\">&amp;&amp;<\/span> curStart <span class=\"token operator\">&lt;<\/span> bestStart<span class=\"token punctuation\">)<\/span><span class=\"token punctuation\">)<\/span> <span class=\"token punctuation\">{<\/span><br \/>\n                        bestLen <span class=\"token operator\">&#061;<\/span> curLen<span class=\"token punctuation\">;<\/span><br \/>\n                        bestStart <span class=\"token operator\">&#061;<\/span> curStart<span class=\"token punctuation\">;<\/span><br \/>\n                    <span class=\"token punctuation\">}<\/span><br \/>\n                <span class=\"token punctuation\">}<\/span><\/p>\n<p>        cout <span class=\"token operator\">&lt;&lt;<\/span> <span class=\"token string\">&#034;Case &#034;<\/span> <span class=\"token operator\">&lt;&lt;<\/span> <span class=\"token operator\">&#043;&#043;<\/span>caseNo <span class=\"token operator\">&lt;&lt;<\/span> <span class=\"token string\">&#034;: &#034;<\/span> <span class=\"token operator\">&lt;&lt;<\/span> bestLen <span class=\"token operator\">&lt;&lt;<\/span> <span class=\"token string\">&#034; &#034;<\/span> <span class=\"token operator\">&lt;&lt;<\/span> bestStart <span class=\"token operator\">&lt;&lt;<\/span> <span class=\"token string\">&#034;\\\\n&#034;<\/span><span class=\"token punctuation\">;<\/span><br \/>\n    <span class=\"token punctuation\">}<\/span><br \/>\n    <span class=\"token keyword\">return<\/span> <span class=\"token number\">0<\/span><span class=\"token punctuation\">;<\/span><br \/>\n<span class=\"token punctuation\">}<\/span><\/p>\n<h3>\u603b\u7ed3<\/h3>\n<p>\u672c\u9898\u7684\u5173\u952e\u5728\u4e8e&#xff1a;<\/p>\n<li>\u5c06\u975e\u5b57\u6bcd\u5b57\u7b26\u4e0e\u5b57\u6bcd\u5206\u79bb&#xff0c;\u53ea\u5173\u5fc3\u5b57\u6bcd\u5e8f\u5217&#xff0c;\u5e76\u8bb0\u5f55\u539f\u4f4d\u7f6e&#xff0c;\u4fbf\u4e8e\u8ba1\u7b97\u539f\u59cb\u5b50\u4e32\u957f\u5ea6\u548c\u8d77\u59cb\u4f4d\u7f6e\u3002<\/li>\n<li>\u4f7f\u7528\u52a8\u6001\u89c4\u5212\u9884\u5904\u7406\u6240\u6709\u533a\u95f4\u7684\u5dee\u5f02\u6570&#xff0c;\u907f\u514d\u91cd\u590d\u8ba1\u7b97&#xff0c;\u5c06\u5224\u65ad\u590d\u6742\u5ea6\u964d\u4e3a <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">O(1)O(1)<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 1em;vertical-align: -0.25em\"><\/span><span class=\"mord mathnormal\" style=\"margin-right: 0.0278em\">O<\/span><span class=\"mopen\">(<\/span><span class=\"mord\">1<\/span><span class=\"mclose\">)<\/span><\/span><\/span><\/span><\/span> \u6bcf\u4e2a\u533a\u95f4\u3002<\/li>\n<li>\u6ce8\u610f\u5dee\u5f02\u6570\u7684\u5b9a\u4e49&#xff1a;\u5bf9\u79f0\u7684\u4e24\u4e2a\u4e0d\u540c\u5b57\u7b26\u8d21\u732e <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">22<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.6444em\"><\/span><span class=\"mord\">2<\/span><\/span><\/span><\/span><\/span> \u4e2a\u4e0d\u540c\u4f4d\u7f6e&#xff0c;\u800c\u975e <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">11<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.6444em\"><\/span><span class=\"mord\">1<\/span><\/span><\/span><\/span><\/span> &#xff0c;\u8fd9\u662f\u5bb9\u6613\u51fa\u9519\u7684\u5730\u65b9\u3002<\/li>\n<li>\u679a\u4e3e\u6240\u6709\u5408\u6cd5\u533a\u95f4\u5e76\u66f4\u65b0\u7b54\u6848&#xff0c;\u540c\u65f6\u6ee1\u8db3\u957f\u5ea6\u4f18\u5148\u3001\u8d77\u59cb\u4f4d\u7f6e\u6b21\u4e4b\u7684\u6392\u5e8f\u8981\u6c42\u3002<\/li>\n<p>\u8be5\u89e3\u6cd5\u5728 <span class=\"katex--inline\"><span class=\"katex\"><span class=\"katex-mathml\">n\u22641000n \\\\le 1000<\/span><span class=\"katex-html\"><span class=\"base\"><span class=\"strut\" style=\"height: 0.7719em;vertical-align: -0.136em\"><\/span><span class=\"mord mathnormal\">n<\/span><span class=\"mspace\" style=\"margin-right: 0.2778em\"><\/span><span class=\"mrel\">\u2264<\/span><span class=\"mspace\" style=\"margin-right: 0.2778em\"><\/span><\/span><span class=\"base\"><span class=\"strut\" style=\"height: 0.6444em\"><\/span><span class=\"mord\">1000<\/span><\/span><\/span><\/span><\/span> 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