题解 | #编号子回文II#

import java.util.*;


public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param s string字符串 
     * @return int整型
     */
    public int longestPalindromeSubseq (String s) {
        // write code here
        int n = s.length();
        int[][] dp = new int[n][n];
        for (int i = 0; i < n; i++) {
            dp[i][i] = 1;
        }
        for (int i = 0, j = 1; i < n && j < n; i++, j++) {
            dp[i][j] = s.charAt(i) == s.charAt(j) ? 2 : 1;
        }
        for (int x = 2; x < n; x++) {
            for (int i = 0, j = x; i < n && j < n; i++, j++) {
                dp[i][j] = Math.max(dp[i + 1][j], dp[i][j - 1]);
                if (s.charAt(i) == s.charAt(j)) {
                    dp[i][j] = Math.max(
                        dp[i][j],
                        dp[i + 1][j - 1] + 2
                    );
                }
            }
        }
        return dp[0][n - 1];
    }
}