pku1942

&l

 Source Code

Problem: 1942 User: henry11Memory: 156K Time: 0MSLanguage: C Result: Accepted

• Source Code

#include<stdio.h>long long Count(long long a, long long b){    if(b>0)    {        return Count(a-1, b-1)*a/b;    }        else    {        return 1;    }    }    int main(){    long long n, m;    while(scanf("%I64d%I64d",t;/span> &n, &m) != EOF && (n||m))    {        printf("%I64d/n", Count(n+m, n>m ? m : n));    }        return 1;}    

一直想不通，（m+n）!/m!n! 这个是怎么来的，排列组合还要复习下才好。