873. 欧拉函数

https://www.acwing.com/problem/content/submission/code_detail/7779824/

AcWing/873/873.cpp

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+#include <bits/stdc++.h>
+
+using namespace std;
+
+int n, x;
+
+int phi(int x) {
+    int res = x;
+    for (int i = 2; i * i <= x; i++) {
+        if (x % i == 0) {
+            res = res / i * (i - 1);
+            while (x % i == 0) x /= i;
+        }
+    }
+    if (x > 1) res = res / x * (x - 1);
+    return res;
+}
+
+int main() {
+    cin >> n;
+    while (n--) {
+        cin >> x;
+        cout << phi(x) << endl;
+    }
+    return 0;
+}