力扣-5.最长回文子串

题目链接

5.最长回文子串

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

小结：双指针可以做居然不超时，但这里还是做了动态规划解法，注意遍历的时候要按照子串长度从小到大遍历，避免跳过。