NumberTheory/Math/EulerPhi.h

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• Last update: 2025-06-11 15:37:14+07:00

Depends on

• template.h

Verified with

• NumberTheory/Math/test/aizu_ntl_1_d_euler_phi.test.cpp

Code

#include "../../template.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;
}

#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;
}

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