Envío 2662

Código

#include <bits/stdc++.h>

#define fi first
#define se second
#define forn(i,n) for(int i=0; i< (int)n; ++i)
#define for1(i,n) for(int i=1; i<= (int)n; ++i)
#define fore(i,l,r) for(int i=(int)l; i<= (int)r; ++i)
#define ford(i,n) for(int i=(int)(n) - 1; i>= 0; --i)
#define fored(i,l,r) for(int i=(int)r; i>= (int)l; --i)
#define pb push_back
#define el '\n'
#define d(x) cout<< #x<< " " << x<<el
#define ri(n) scanf("%d",&n)
#define sz(v) ((int)v.size())
#define all(v) v.begin(),v.end()
#define allr(v) v.rbegin(),v.rend()

using namespace std;

typedef long long ll;
typedef double ld;
typedef pair<int,int> ii;
typedef pair<char,int> pci;
typedef tuple<int, int, int> tiii;
typedef pair<ll,ll> pll;
typedef vector<int> vi;

const int inf = 1e9;
const int nax = 1e5+200;
const ld pi = acos(-1);
const ld eps= 1e-9;

int dr[] = {1,-1,0, 0,1,-1,-1, 1};
int dc[] = {0, 0,1,-1,1, 1,-1,-1};


vector<int> get_phi(string &s) { // O(|s|)
  int j = 0, n = sz(s);
  vi pi(n);
  for1(i,n-1){
    while (j > 0 && s[i] != s[j]) j = pi[j-1];
    j += (s[i] == s[j]);
    pi[i] = j;
  }
  return pi;
}

int main(){
  ios_base::sync_with_stdio(false);
  cin.tie(NULL); cout.tie(NULL);
  cout<< setprecision(20)<< fixed;
  string s;
  cin>> s;
  vi p = get_phi(s);
  int n = sz(s);
  cout<< p.back() <<el;
}