poj2249

简单题

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
using namespace std;

int com(int n, int r)
{
    if (n - r < r)
        r = n - r;
    int i , j;
    long long s = 1;
    for (i = 0, j = 1; i < r; i++)
    {
        s *=(n - i);
        for (; j <= r && s % j == 0; j++)
            s /= j;
    }
    return (int)s;
}

int main()
{
    //freopen("t.txt", "r", stdin);
    int n, k;
    while (scanf("%d%d", &n, &k), n | k)
        printf("%d\n", com(n, k));
    return 0;
}