Submission #736418

#	Time	Username	Problem	Language	Result	Execution time	Memory
736418		hollwo_pelw	The Xana coup (BOI21_xanadu)	C++17	100 / 100	68 ms	18432 KiB

xanadu

#include <bits/stdc++.h>
// #include <ext/pb_ds/assoc_container.hpp>
// #include <ext/pb_ds/trie_policy.hpp>
// #include <ext/rope>

using namespace std;
// using namespace __gnu_cxx;
// using namespace __gnu_pbds;

void Hollwo_Pelw();

signed main(){
#ifndef hollwo_pelw_local
	if (fopen(".inp", "r"))
		assert(freopen(".inp", "r", stdin)), assert(freopen(".out", "w", stdout));
#else
	using namespace chrono;
	auto start = steady_clock::now();
#endif
	cin.tie(0), cout.tie(0) -> sync_with_stdio(0);
	int testcases = 1;
	// cin >> testcases;
	for (int test = 1; test <= testcases; test++){
		// cout << "Case #" << test << ": ";
		Hollwo_Pelw();
	}
#ifdef hollwo_pelw_local
	auto end = steady_clock::now();
	cout << "\nExecution time : " << duration_cast<milliseconds> (end - start).count() << "[ms]" << endl;
#endif
}

const int N = 1e5 + 5, inf = 1e9;

int n, a[N], dp[N][2][2];
vector<int> adj[N];

void dfs(int u, int p) {
	for (int i = 0; i < 2; i++)
		dp[u][i][a[u] ^ i] = i;

	for (int v : adj[u]) if (v != p) {
		dfs(v, u);
		for (int i = 0; i < 2; i++) {
			int dpu0 = dp[u][i][0], dpu1 = dp[u][i][1];
			dp[u][i][0] = min({dpu0 + dp[v][0][i], dpu1 + dp[v][1][i], inf});
			dp[u][i][1] = min({dpu0 + dp[v][1][i], dpu1 + dp[v][0][i], inf});
		}
	}
}

void Hollwo_Pelw(){
	memset(dp, 0x3f, sizeof dp);
	cin >> n;
	for (int i = 1, u, v; i < n; i++) {
		cin >> u >> v;
		adj[u].push_back(v);
		adj[v].push_back(u);
	}
	for (int i = 1; i <= n; i++)
		cin >> a[i];
	dfs(1, 0);
	int res = min(dp[1][0][0], dp[1][1][0]);
	if (res > n)
		cout << "impossible\n";
	else
		cout << res << '\n';
}

• Subtask 1: 5 / 5
• Subtask 2: 15 / 15
• Subtask 3: 10 / 10
• Subtask 4: 40 / 40
• Subtask 5: 30 / 30