Finding Periods.cpp

#include<bits/stdc++.h>
using namespace std;
#define INF 2047483647
#define INFL 9223372036854775807
#define ll long long
#define pii pair<int,int>
#define pII pair<ll,ll>
#define vi vector<int>
#define vii vector<pii>
#define vI vector<ll>
#define VII vector<pII>
#define F first
#define S second
#define mp make_pair
#define pb push_back
#define ull unsigned long long
#define M 1000000007
#define FASTIO ios_base::sync_with_stdio(false);cin.tie(NULL); cout.tie(NULL);
#define take(x) scanf("%d",&x)
#define DE(x) printf("\ndebug %d\n",x);
#define vout(x) for(int i=0;i<x.size();i++) printf("%d ",x[i]);
#define pie acos(-1)
#define MOD 998244353

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
int my_rand(int l, int r){return uniform_int_distribution<int>(l,r) (rng);}

int Set(int N,int pos){return N=N | (1<<pos);}
int reset(int N,int pos){return N= N & ~(1<<pos);}
bool check(int N,int pos){return (bool)(N & (1<<pos));}


vector<int> z_function(string s) {
    int n = (int) s.length();
    vector<int> z(n);
    for (int i = 1, l = 0, r = 0; i < n; ++i) {
        if (i <= r)
            z[i] = min (r - i + 1, z[i - l]);
        while (i + z[i] < n && s[z[i]] == s[i + z[i]])
            ++z[i];
        if (i + z[i] - 1 > r)
            l = i, r = i + z[i] - 1;
    }
    return z;
}

int main(){
    string S;
    cin>>S;
    int n = S.size();
    auto z = z_function(S);
    for(int i=1;i<=n;i++){
        bool flag = true;
        for(int j=i;j<n;j+=i){
            if( j+i<n and z[j]<i ) flag = false;
            else if( j+i>=n and j+z[j]<n ) flag = false;
        }
        if(flag) cout<<i<<" ";
    }
}