力扣-5-最长回文子串

public String longestPalindrome(String s) {
    int len = s.length();
    if(len < 2) return s;
    int maxLen = 1;
    int begin = 0;

    int[][] dp = new int[len][len];//dp[i][j]表示s[i,j]是否是回文串，1是，0不是
    char[] charArray = s.toCharArray();

    for(int i = 0;i < len;i++){
        dp[i][i] = 1;
    }

    for(int j = 1;j<len;j++){
        for(int i = 0;i<j;i++){
            if(charArray[i] != charArray[j])
                dp[i][j] = 0;
            else{
                if(j - i < 3){
                    dp[i][j] = 1;
                }else{
                    dp[i][j] = dp[i+1][j-1];//大子串参考小子串的判断结果
                }
            }

            if(dp[i][j] == 1 && j - i + 1 > maxLen){
                maxLen = j - i + 1;
                begin = i;
            }
        }
    }
    return s.substring(begin,begin+maxLen);
}