804. n的阶乘

https://www.acwing.com/problem/content/submission/code_detail/14063689/

AcWing/804/804.cpp

@@ -0,0 +1,19 @@
+#include <iostream>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+int n, res = 1;
+
+int main() {
+    std::ios::sync_with_stdio(false);
+
+    cin >> n;
+
+    while (res *= n--, n) {}
+
+    cout << res << endl;
+
+    return 0;
+}