Leetcode: Longest Palindromic Substring. java

Given
a string S,
find the longest palindromic substring in S.
You may assume that the maximum length of S is
1000, and there exists one unique longest palindromic substring.

动态规划

public class Solution {

    public String longestPalindrome(String s) {

        if (s == null || s.length() == 0) return "";

        int n = s.length();

        int max = 0, start = 0, end = 0;

        boolean[][] c = new boolean[n][n];

        for (int i = 0; i < n; i++) {

            for (int j = 0; j < n; j++) {

                c[i][j] = i >= j ? true : false;

            }

        }

        //c[i][j] 记录从第i个到第j个是不是回文。

        for (int j = 1; j < n; j++) {

            for (int i = 0; i < j; i++) {

                if (s.charAt(i) == s.charAt(j) && c[i+1][j-1]) {

                    c[i][j] = true;

                    if (j - i + 1 > max) {

                        max = j - i + 1;

                        start = i;

                        end = j;

                    }

                }

                else

                    c[i][j] = false;

            }

        }

        return s.substring(start, end+1);

    }

}

Leetcode: Longest Palindromic Substring. java