NumberTheory/Aizu/aizu_ntl_1_d_euler_phi.test.cpp

• View this file on GitHub
• Last update: 2025-10-07 00:37:04+07:00
• Problem: https://onlinejudge.u-aizu.ac.jp/courses/library/6/NTL/1/NTL_1_D

Depends on

• NumberTheory/Math/EulerPhi.h
• template.h

Code

#define PROBLEM "https://onlinejudge.u-aizu.ac.jp/courses/library/6/NTL/1/NTL_1_D"

#include "../../template.h"
#include "../Math/EulerPhi.h"

void solve() {
    ll n; cin >> n;
    cout << eulerPhi(n) << '\n';
}

#line 1 "NumberTheory/Aizu/aizu_ntl_1_d_euler_phi.test.cpp"
#define PROBLEM "https://onlinejudge.u-aizu.ac.jp/courses/library/6/NTL/1/NTL_1_D"

#line 2 "template.h"

#include <bits/stdc++.h>
using namespace std;
 
#define ll long long
#define MOD (ll)(1e9+7)
#define all(x) (x).begin(),(x).end()
#define unique(x) x.erase(unique(all(x)), x.end())
#define INF32 ((1ull<<31)-1)
#define INF64 ((1ull<<63)-1)
#define inf (ll)1e18

#define vi vector<int>
#define pii pair<int, int>
#define pll pair<ll, ll>
#define fi first
#define se second

const int mod = 998244353;

void solve();

int main(){
    ios_base::sync_with_stdio(false);cin.tie(NULL);
    // cin.exceptions(cin.failbit);
    // int t; cin >> t;
    // while(t--)
        solve();
    cerr << "\nTime run: " << 1000 * clock() / CLOCKS_PER_SEC << "ms" << '\n';
    return 0;
}
#line 2 "NumberTheory/Math/EulerPhi.h"

ll eulerPhi(ll n) {
    if (n == 0) return 0;
    ll ans = n;
    for (ll i = 2; i*i <= n; i++) {
        if (n % i == 0) {
            ans -= ans / i;
            while (n % i == 0) n /= i;
        }
    }
    if (n > 1) ans -= ans / n;
    return ans;
}

vector<int> phi_from_1_to_n(int n) {
    vector<int> phi(n + 1);
    iota(all(phi), 0);
    
    for (int i = 2; i <= n; i++) {
        if (phi[i] == i) {
            for (int j = i; j <= n; j += i) {
                phi[j] -= phi[j] / i;
            }
        }
    }
    return phi;
}

// phi(a * b) = phi(a) * phi(b) / phi(gcd(a, b)) * gcd(a, b)
// int gcd = __gcd(a, b);
// int phi[a*b] = (1ull * phi[a] * phi[b] / phi[gcd] * gcd) % mod;
#line 5 "NumberTheory/Aizu/aizu_ntl_1_d_euler_phi.test.cpp"

void solve() {
    ll n; cin >> n;
    cout << eulerPhi(n) << '\n';
}

Back to top page