'commit'

TangDou/AcWing/Math/Euler.cpp

@@ -0,0 +1,26 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+/**
+ * 功能：欧拉函数 互质的概念理解：gcd(x,y)=1
+ * @param x
+ * @return
+ */
+int phi(int x) {
+    int res = x;
+    for (int i = 2; i <= x / i; 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() {
+    for (int i = 1; i <= 10; i++)
+        cout << "i=" << i << " phi[" << i << "]=" << phi(i) << endl;
+    //以9为例，与9形成gcd(x,9)=1的x共有6个，分别是(1,2,4,5,7,8)
+    return 0;
+}