LCS

#include<bits/stdc++.h>

using namespace std;

int main()
{
    string s1, s2;
    int n1, n2;
    cin>>s1>>s2;
    n1=s1.size();
    n2=s2.size();

    int table[n2+2][n1+2];

    for(int i=0;i<=n1;i++) table[0][i]=0;
    for(int i=0;i<=n2;i++) table[i][0]=0;

    for(int i=1;i<=n2;i++){
        for(int j=1;j<=n1;j++){
            if(s2[i-1]==s1[j-1]){
                table[i][j]=table[i-1][j-1]+1;
            }
            else{
                table[i][j]=max(table[i][j-1],table[i-1][j]);
            }
        }
    }

    int sz=table[n2][n1];
    cout<<"Length of LCS "<<sz<<endl;
    vector<char> v;
    int x=table[n2][n1];
    int i=n2,j=n1;


    while(1){
        if(table[i][j]==0) break;
        if(table[i][j]==(table[i-1][j-1]+1) && s1[j-1]==s2[i-1]){
            v.push_back(s1[j-1]);
            i--;
            j--;
        }
        else{
            if(table[i][j]==table[i][j-1]){
                j--;
            }
            else{
                i--;
            }
        }
    }

    cout<<"Subsequence is ";
    for(int i=v.size()-1;i>=0;i--) cout<<v[i];
    cout<<endl;

    return 0;
}