Submission #881396

#	Time	Username	Problem	Language	Result	Execution time	Memory
881396		vjudge1	Star Trek (CEOI20_startrek)	C++17	0 / 100	1 ms	2908 KiB

startrek

// In the Name of Allah

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

#define int long long
#define F first
#define S second
#define pii pair<int, int>
#define pb push_back
#define pp pop_back
#define all(x) x.begin(), x.end()
#define unq(x) sort(all(x)), x.resize(unique(all(x)) - x.begin())

const int N = 1e5 + 12, mod = 1'000'000'000 + 7;
vector<int> g[N];
int n, d, c[2];

int bp(int x, int y) {
	if (y < 2) return y? x : 1;
	int tmp = bp(x, y / 2);
	tmp = tmp * tmp % mod;
	return (y & 1)? tmp * x % mod : tmp;
}
/*
int dfs(int u, int par) {
	bool res = false;
	for (auto i: g[u])
		if (i != par)
			res |= dfs(i, u);
	c[!res]++;
	return !res;
}
*/
void ip() {
	cin >> n >> d;
	for (int i = 1; i < n; i++) {
		int u, v;
		cin >> u >> v;
		u--, v--;
		g[u].pb(v);
		g[v].pb(u);
	}
}

void solve() {
	if (n == 2)
		cout << bp(2, d + 1);
}

int32_t main() {
	ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
	ip(), solve();
	return 0;
}

• Subtask 1: 0 / 0
• Subtask 2: 0 / 7
• Subtask 3: 0 / 8
• Subtask 4: 0 / 15
• Subtask 5: 0 / 15
• Subtask 6: 0 / 20
• Subtask 7: 0 / 20
• Subtask 8: 0 / 15