组合数计算，防止溢出

#include <iostream>using namespace std;typedef  long long ll;ll C(ll n, ll m){    ll res = 1;    for(ll i = 1; i <= m; ++i)        res = res*(n-m+i)/i;    return res;}int main(){    cout << C(100,15) << endl;    return 0;}

参考：http://blog.csdn.net/perfumekristy/article/details/8713083