zfunk

#include <bits/stdc++.h>
#define MAX 100007

using namespace std;

int z[MAX];

void func(string s){
    int l = 0, r = 0;
    for(int i = 1; i < s.size(); i++){
        z[i] = max(0, min(z[i-l], r-i+1));
        while(i+z[i] < s.size() && s[z[i]] == s[i+z[i]]){
            l = i; r = i+z[i]; z[i]++;
        }
    }
}