$ C_{a}^{b}=C_{a-1}^{b-1}+C_{a-1}^{b} $

C++ 代码

/* 
 * @Author: lzyws739307453 
 * @Language: C++ 
 */
#include <bits/stdc++.h>
using namespace std;
const int MAXN = 2000, MAXM = 2005;
const int MOD = 1e9 + 7;
int C[MAXM][MAXM];
void Com_Num(int n) {
    C[0][0] = 1;
    for (int i = 0; i <= n; i++) {
        C[i][0] = 1;
        for (int j = 1; j <= i; j++)
            C[i][j] = (C[i - 1][j - 1] + C[i - 1][j]) % MOD;
    }
}
int main() {
    int t;
    Com_Num(MAXN);
    scanf("%d", &t);
    while (t--) {
        int a, b;
        scanf("%d%d", &a, &b);
        printf("%d\n", C[a][b]);
    }
    return 0;
}