poj1942求组合数

就是一求组合数的问题。

#include <iostream>
#include <algorithm>

using namespace std;

#define ULL unsigned long long int

int main()
{
    ULL a, b;
    while (cin >> a >> b && (a || b))
    {
        if (b > a) swap(a, b);
        ULL s = 1, i, j;
        for (i = a + 1, j = 1; i <= a + b; i++, j++)
        {
            s = s * i / j;
            cout<<i<<" "<<j<<" "<<s<<endl;
        }
        cout << s << endl;
    }
}

或者

/*强制类型转换输出*/

//Memory Time 
//220K   0MS 

#include<iostream>
#include<math.h>
using namespace std;

/*Compute (n+m)C min{n,m}*/

unsigned comp(unsigned n,unsigned m)
{
	unsigned a=m+n;
	unsigned b=(m<n?m:n);
	double cnm=1.0;
	while(b>0)
		cnm*=(double)(a--)/(double)(b--);

    cnm+=0.5;      //double转unsigned会强制截断小数，必须先四舍五入
	return (unsigned)cnm;
}

int main(void)
{
	unsigned m,n;
	while(true)
	{
		cin>>m>>n;
		if(!m && !n)//承认这题的猥琐吧！竟然有其中一边为0的矩阵，一定要&&，用||会WA
			break;

		cout<<comp(n,m)<<endl;
	}
	return 0;
}