Longest common substring

// longest common subsequence
// [1 ,2 ,3, 4]
// subsequnce (order matters but maybe not continuous)
// substring or subarray .. (need to be contigous)
// subset same as subsequence ..
int solve(string s1 , string s2){
    int sa = s1.length();
    int sb = s2.length();
    vector<vector<int>> dp (sa+1 ,vector<int>(sb+1,0));


    for(int a=1;a<=sa;a++){
        for(int b=1;b<=sb;b++){
            if(s1[a-1] == s2[b-1]){
            dp[a][b] = 1 + dp[a-1][b-1];
            }else{
            dp[a][b] = 0;
            }
        }
    }
    int mx = 0;
    for(int a=0;a<=sa;a++){
        for(int b=0;b<=sb;b++){
            mx = max(mx,dp[a][b]);
        }
    }
    return mx;
}