SMMR-108: Magic Spell II

#include<bits/stdc++.h>
using namespace std;
string a,b,ans;
int dp[2020][2020];
void find(int n,int m){
    int mx=0,st,en;
    for(int i=0;i<=n;i++){
        for(int j=0;j<=m;j++){
            if(i==0||j==0){dp[i][j]=0;}
            else if(a[i-1]==b[j-1]){
                dp[i][j]=1+dp[i-1][j-1];
                if(mx<dp[i][j]){
                    mx=dp[i][j];
                    st=i; en=j;
                }
            }
            else{dp[i][j]=0;}
        }
    }
    while(dp[st][en]!=0){
        ans=a[st-1]+ans; st--;en--;
    }
    cout<<ans;
    return;
}

int main(){
    cin>>a; cin>>b;

    find(a.size(),b.size());

    return 0;
}