Cod sursă (job #530130)

#include <bits/stdc++.h>

using namespace std;
char sir[500005];
int pref[500005];
int main()
{
    ifstream cin("bart.in");
    ofstream cout("bart.out");

    int n,i,k;
    cin>>sir+1;
    n=strlen(sir+1);
    k=0;
    pref[1]=0;
    for(i=2;i<=n;i++){
        while(k>0 && sir[k+1]!=sir[i])
            k=pref[k];
        if(sir[k+1]==sir[i])
            k++;
        pref[i]=k;
    }
    for(i=1;i<=n-pref[n];i++){
        cout<<sir[i];
    }
    return 0;
}