main.cpp

#include <iostream>
#include <algorithm>
#include <string>
#include <vector>
using namespace std;

// dp
class Solution {
public:
    int longestPalindromeSubseq(string s) {
        int n = s.size();
        vector<vector<int>> dp(n, vector<int>(n,0));
        for(int i = n-1; i >= 0; i--)
        {
            dp[i][i] = 1;
            for(int j = i+1; j < n; ++j)
            {
                if(s[i] == s[j])
                {
                    dp[i][j] = dp[i+1][j-1] + 2;
                }
                else
                {
                    dp[i][j] = max(dp[i+1][j], dp[i][j-1]);
                }
            }
        }
        return dp[0][n-1];
    }
};

int main()
{
    Solution s;
    cout << s.longestPalindromeSubseq("bbbab") << endl;
    return 0;
}