leetcode：Longest Palindromic Substring

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最长公共子字符串

定义状态dp[i][j],表示子字符串Si-Sj是否回文串

那么dp[i][j] = dp[i+1][j - 1] && s(i) == s(j)

public class Solution {    public String longestPalindrome(String s) {        boolean[][] dp = new boolean[s.length() + 1][s.length() + 1];        int maxLen = 0;        int site = 0;        for(int i = 0; i < s.length() - 1; ++i){            dp[i][i] = true;            dp[i][i + 1] = s.charAt(i) == s.charAt(i + 1);            if(dp[i][i + 1] && maxLen == 0){                site = i;                maxLen = 1;            }        }        dp[s.length() - 1][s.length() - 1] = true;                        for(int i = 2; i < s.length(); ++i){            for(int j = 0; j < i - 1; ++j){                if(s.charAt(i) == s.charAt(j) &&  dp[j + 1][ i - 1]){                    dp[j][i] = true;                    if(i - j > maxLen){                        site = j;                        maxLen = i - j;                    }                }            }        }        return s.substring(site, site + maxLen + 1);    }}

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