題目如下：

解題思路：很經典的動態規劃題目，但是用python會超時，只好用C++了。

代碼如下：

class Solution {
public:
    int longestPalindromeSubseq(string s) {
        int dp[1001][1001] = {0};
        int res = 1;
        for (int i = s.length()-1;i >=0;i--){
            for (int j = i+1;j<s.length();j++){
                dp[i][i] = 1;
                
 
if (s[i] == s[j]){
                    dp[i][j] = dp[i][j] > dp[i+1][j-1]+2 ? dp[i][j] :dp[i+1][j-1]+2; 
                }
                else{
                    dp[i][j] = dp[i][j-1] > dp[i+1][j] ? dp[i][j-1] : dp[i+1][j];
                }
                res = res > dp[i][j] ? res : dp[i][j];
            }
            
        }
        
 
return res;
    }
};

【leetcode】516. Longest Palindromic Subsequence