poj1942 Paths on a Grid

题意很好理解，只是数据有点大，是用排列组合的知识，为了减小数据量，阶乘采用间接求得！注意下就可以了，还有对double数据要采用四舍五入的方法。

#include<iostream>#include<cstdio>#include<cmath>using namespace std;void fun(unsigned int n,unsigned int m){double s=1.0,t;unsigned int i,b;b=n>m?m:n;for(i=1; i<=b; i++){t=((1.0*(n+m+1-i))/(1.0*(b+1-i)));s=s*t ;}s+=0.5;printf("%u\n",(unsigned int)s);}int main(){unsigned int n,m;while(1){        scanf("%u%u",&n,&m);if(n==0 && m==0)break;fun(n,m);}return 0;}