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;
}