题目链接：求组合数 I

#include <iostream>
#include <algorithm>using namespace std;const int mod = 1e9 + 7;int n;
const int N = 2010;
int c[N][N];void init()
{for(int i = 0; i < N; i ++)for(int j = 0; j <= i; j++)if(!j) c[i][j] = 1;else c[i][j] = (c[i - 1][j] + c[i - 1][j - 1]) % mod;
}int main()
{init();cin >> n;while(n --){int a, b;scanf("%d%d", &a, &b);cout << c[a][b] << endl;}return 0;
}