516. Longest Palindromic Subsequence

Given a string s, find the longest palindromic subsequence's length in s. You may assume that the maximum length of s is 1000.
Example 1:
Input:
"bbbab"
Output:
4
One possible longest palindromic subsequence is "bbbb".

Example 2:
Input:
"cbbd"
Output:
2
One possible longest palindromic subsequence is "bb".
求最长回文子序列

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动态规划问题，因为有“讨价还价”。
注意j从i+1开始。

class Solution {
    public int longestPalindromeSubseq(String s) {
        int n = s.length();
        int[][] dp = new int[n][n];
        for(int i=n-1;i>=0;i--){
            dp[i][i]=1;
            // j start from i+1
            for(int j=i+1;j