#include <stdio.h>

int C(int a,int b)
{
    if(a==b||b==0)
        return 1;
    else
        return C(a-1,b)+C(a-1,b-1);
}
int main()
{
    int n,k;
    int s;
    while(scanf("%d%d",&n,&k)!=EOF)
    {
       s=C(n,k);
       printf("%d\n",s);
    }
    return 0;
}
--------------------- 
原文：https://blog.csdn.net/rating_/article/details/84034728