题目链接:点击这里
#include<iostream>
#include<cstdio>
#include<algorithm>
using namespace std;
const int N = 2010, mod = 1e9 + 7;
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();
int n;
scanf("%d", &n);
while(n--)
{
int a, b;
scanf("%d%d", &a, &b);
printf("%d\n", c[a][b]);
}
return 0;
}