Envío 2065

Código

#include <bits/stdc++.h>

using namespace std;

#define endl '\n'
#define ll long long
#define pii pair<int, int>
const int maxi = 100000;
const ll M = 999727999;
const ll P = 1610612741;
ll hasha[maxi];
ll pott[maxi];

int main(){
  ios::sync_with_stdio(0); cin.tie(0); 
  //USING HASHING 
  string s;
  cin>>s;
  ll pot =1;
  for(int i=0;i<s.size(); i++){
    hasha[i+1] =(hasha[i]+(pot*(s[i]-'a'+1)))%M;
    pott[i+1] = pot;
    pot = (pot*P)%M;
  }
  int j=s.size();
  int ans = 0;
  for(int i=1;i<s.size();i++){
    if((hasha[i]*pott[j-i+1])%M==((hasha[j]-hasha[j-i]+M)%M)){
      ans=i;
    }
  }
  cout<<ans<<endl;
  return 0;
}