Envío 4099

Código

/// Write by Daniel Perez .PERAPRO
#include<bits/stdc++.h>

using namespace std;
#define fast_io ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
using vi=vector<int>;
using pii=pair<int,int>;
#define pb push_back
#define ff first
#define ss second
typedef long long ll;
typedef unsigned long long ull;
char el = '\n';

ostream& operator<<(ostream& os, const vector<int> &v){
    for(auto const &i: v){
        os<<i<<" ";
    }
    os<<endl;
    return os;
}
string yes="YES";
string no="NO";

int main(){
	fast_io;
	string s;
	cin>>s;
	int n=s.size();
	vi ps(n);
	for(int i=1;i<n;i++){
	    int j=ps[i-1];
	    while(s[j] != s[i] && j>0){
	        j=ps[j-1];
	    }
	    if(s[i]==s[j]){
	        ps[i]=j+1;
	    }
	}
	//cout<<ps;
	cout<<ps[n-1]<<el;
}