题解 | #牛牛的排列数#
牛牛的排列数
https://www.nowcoder.com/practice/9ca1c236cdbf46da9e08e1f510808625
#include <stdio.h> double f(int x); int main() { int n = 0, m = 0; double r = 0; scanf("%d%d", &n, &m); if (n < m) printf("0"); else { r = f(n) / f(n - m); printf("%.0lf", r); } return 0; } double f(int x) { if (x == 1 || x == 0) return 1; else return x * f(x - 1); }