leetcode5最长回文子串

思路

s37 如果是回文串，那么s46一定也是，然后在需要判断两个顶点

需要考虑两个特殊情况

1. abcd a、b、c、d都可以
2. aa

代码

public String longestPalindrome(String s) {
        int[][] map = new int[1001][1001];
        int[] result = new int[]{0,0};
        for (int i = 0; i < s.length(); i++) {
            map[i][i] = 1;
        }
        for (int i = 0; i+1 < s.length(); i++) {
            if (s.charAt(i) == s.charAt(i+1)){
                result[0] = i;
                result[1] = i+1;
                map[i][i+1] = 1;
            }
        }
        for (int i = 2 ; i < s.length(); i++){
            for (int j = 0; j+i < s.length(); j++) {
                if (map[j+1][j+i-1] == 1 && s.charAt(j) == s.charAt(j+i)){
                    result[0] = j;
                    result[1] = j+i;
                    map[j][j+i] = 1;
                }
            }
        }
        return s.substring(result[0], result[1]+1);
    }