Submission #999040

#	Time	Username	Problem	Language	Result	Execution time	Memory
999040		vjudge1	Sumtree (INOI20_sumtree)	C++17	10 / 100	63 ms	41640 KiB

Main

#include <bits/stdc++.h>

using namespace std;

#define int long long

const int MXN = 1e6 + 5;
const int mod = 1e9 + 7;

int n, r;
vector<int> adj[MXN];
int f[MXN];

int pw(int a, int b, int c)
{
	a %= c;
	int res = 1;
	while (b)
	{
		if (b & 1) res = (res * a) % mod;
		a = (a * a) % mod;
		b >>= 1;
	}
	return res;
}

int nck(int n, int k)
{
	if (min(n, k) < 0 || k > n) return 0;
	return (f[n] * pw((f[n - k] * f[k]) % mod, mod - 2, mod)) % mod;
}

signed main()
{
	ios::sync_with_stdio(0);
	cin.tie(0);
	f[0] = 1;
	for (int i = 1; i < MXN; i++) f[i] = (f[i - 1] * i) % mod;
	cin >> n >> r;
	for (int i = 1; i < n; i++)
	{
		int u, v;
		cin >> u >> v;
		adj[u].push_back(v);
		adj[v].push_back(u);
	}
	int q, res = 0;
	cin >> q;
	cout << nck(n + r - 1, r) << '\n';
}

Compilation message (stderr)

Main.cpp: In function 'int main()':
Main.cpp:47:9: warning: unused variable 'res' [-Wunused-variable]
   47 |  int q, res = 0;
      |         ^~~

• Subtask 1: 10 / 10
• Subtask 2: 0 / 20
• Subtask 3: 0 / 20
• Subtask 4: 0 / 20
• Subtask 5: 0 / 30