class Solution {
public:
    vector<vector<int>>dp;
    int longestCommonSubsequence(string s1, string s2) {

        int n = s1.size();
        int m = s2.size();

       dp = vector<vector<int>>(n+1 , vector<int>(m+1 , -1));
        for(int i=0;i<=n;i++)
        {
            for(int j=0;j<=m;j++)
            {
                dp[i][j]=-1;
            }
        }


        solve(s1,s2,n,m);
        return dp[n][m];

    }

    int solve(string& s1 , string& s2 ,int n,int m)
    {

        if(n==0 || m==0)return 0;
        if(dp[n][m]!=-1)return dp[n][m];

        if(s1[n-1] == s2[m-1]){
            dp[n][m] = 1 + solve(s1,s2,n-1,m-1);
        }
        else{

            dp[n][m] = max(solve(s1,s2,n-1,m) , solve(s1,s2,n,m-1));
        }

        return dp[n][m];
    }
};

class Solution {
public:
    int longestCommonSubsequence(string s1, string s2) {

        int n = s1.size();
        int m = s2.size();

        int dp[n+1][m+1];
        for(int i=0;i<=n;i++)
        {
            for(int j=0;j<=m;j++)
            {
                dp[i][j]=0;
            }
        }


        for(int i=1;i<=n;i++)
        {
            for(int j=1;j<=m;j++)
            {
                if(s1[i-1]==s2[j-1])
                {
                    dp[i][j] = max({dp[i][j],dp[i-1][j-1]})+1;
                }
                else {
                    dp[i][j] = max({dp[i-1][j],dp[i][j-1],dp[i][j]});
                }
            }
        }


        return dp[n][m];

    }
};