百（垃）度（圾）之星初赛B hdu6114

Chess

题意：中文题

思路：其实就是在n个格子上放m个棋子（n>=m）（xjb套Lucas的板子...

AC代码：

#include "iostream"
#include "string.h"
#include "stack"
#include "queue"
#include "string"
#include "vector"
#include "set"
#include "map"
#include "algorithm"
#include "stdio.h"
#include "math.h"
#pragma comment(linker, "/STACK:102400000,102400000")
#define ll long long
#define endl ("\n")
#define bug(x) cout<<x<<" "<<"UUUUU"<<endl;
#define mem(a,x) memset(a,x,sizeof(a))
#define mp(x,y) make_pair(x,y)
#define pb(x) push_back(x)
#define ft first
#define sd second
#define lrt (rt<<1)
#define rrt (rt<<1|1)
using namespace std;
const long long INF = 1e18+1LL;
const int inf = 1e9+1e8;
const int N=1e5+100;
const ll mod=1e9+7;ll     exp_mod(ll a, ll b, ll p){ll res = 1;while(b != 0){if(b&1) res = (res * a) % p;a = (a*a) % p;b >>= 1;}return res;
}
ll Comb(ll a, ll b, ll p){if(a < b)   return 0;if(a == b)  return 1;if(b > a - b)   b = a - b;ll ans = 1, ca = 1, cb = 1;for(ll i = 0; i < b; ++i){ca = (ca * (a - i))%p;cb = (cb * (b - i))%p;}ans = (ca*exp_mod(cb, p - 2, p)) % p;return ans;
}
ll C(int n, int m, int p){ll ans = 1;while(n&&m&&ans){ans = (ans*Comb(n%p, m%p, p)) % p;n /= p;m /= p;}return ans;
}int n,m;
int main(){ios::sync_with_stdio(0),cin.tie(0),cout.tie(0);int T; cin>>T;while(T--){cin>>n>>m;if(n<m ) swap(n,m);cout<<C(n,m,mod)<<endl;}return 0;
}