hdu 1286 找新朋友 （容斥原理 || 欧拉函数）

#include <cstdio>
#include <iostream>
#include <algorithm>
#include <cstring>
#include <vector>

using namespace std;

const int N = 33333;

int last
;
void pre() {
last[1] = 1;
for (int i = 2; i < N; i++) {
if (!last[i]) {
for (int j = i; j < N; j += i) {
last[j] = i;
}
}
}
//    for (int i = 0; i < 20; i++) cout << last[i] << endl;
}

int phi(int n) {
int ret = 1;
while (n > 1) {
int tmp = last
;
//        cout << tmp << endl;
ret *= tmp - 1;
n /= last
;
while (tmp == last
) {
ret *= tmp;
n /= last
;
}
}
return ret;
}

int main() {
pre();
int T, n;
cin >> T;
while (T-- && cin >> n) cout << phi(n) << endl;
return 0;
}