Shared code

#include <bits/stdc++.h>
using namespace std; 

typedef long long ll;  

// Nhập vào n, k. In ra nCk mod 10^9 + 7.  

// nCk = n! / [(n - k)! * k!]

const int N = 1e6 + 5;  
const int MOD = 1e9 + 7;  

ll fact[N], inv_fact[N];  

ll binpow(ll a, ll b) {
	ll ans = 1;  
	for (; b > 0; b >>= 1) {
		if (b & 1) ans = ans * a % MOD;    
		a = a * a % MOD; 
	}
	return ans; 
}

ll inv(int x) {
	return binpow(x, MOD - 2);   
}

void precompute() {
	fact[0] = 1;  
	// i! = (i - 1)! * i  
	for (int i = 1; i < N; i++) fact[i] = fact[i - 1] * i % MOD;   

	inv_fact[N - 1] = inv(fact[N - 1]);   
	for (int i = N - 2; i >= 0; i--) inv_fact[i] = inv_fact[i + 1] * (i + 1) % MOD;   
}

ll nCk(int n, int k) { // n >= k 
	if (n < k) return 0;   
	return fact[n] * inv_fact[n - k] % MOD * inv_fact[k] % MOD;  
}

int main() {
	ios::sync_with_stdio(0); cin.tie(0);  
	int t; cin >> t;

	precompute();   

	while (t--) {
		int n, k; 
		cin >> n >> k;  

		cout << nCk(n, k) << '\n'; 
	}
}