Submission #848831

#	Time	Username	Problem	Language	Result	Execution time	Memory
848831		TAhmed33	The Xana coup (BOI21_xanadu)	C++98	100 / 100	107 ms	22864 KiB

xanadu

#include <bits/stdc++.h>
using namespace std;
#define int long long
const int MAXN = 1e5 + 25;
vector <int> adj[MAXN];
bool ok[MAXN];
int dp[MAXN][2][2], n;
int ans (int pos, int par, int x, int y) {
	int &ret = dp[pos][x][y];
	if (ret != -1) return ret;
	if (adj[pos].size() == 1 && par != -1) {
		if (ok[pos] ^ x ^ y) {
			return ret = 1e9;
		}
		return ret = y;
	}
	int p[2] = {}; //subset which adds even parity
	int q[2] = {}; //subset which adds odd parity
	int cnt = 0;
	for (auto i : adj[pos]) {
		if (i == par) continue;
		cnt++;
		if (cnt == 1) {
			q[0] = ans(i, pos, y, 1);
			p[0] = ans(i, pos, y, 0);
			continue;
		}
		p[1] = min(ans(i, pos, y, 0) + p[0], ans(i, pos, y, 1) + q[0]);
		q[1] = min(ans(i, pos, y, 0) + q[0], ans(i, pos, y, 1) + p[0]);
		q[0] = q[1]; p[0] = p[1];
	}
	bool i = ok[pos] ^ x ^ y;
	if (i) return ret = y + q[0];
	else return ret = y + p[0];
}
signed main () {
	memset(dp, -1, sizeof(dp));
	cin >> n;
	for (int i = 1; i < n; i++) {
		int a, b;
		cin >> a >> b;
		adj[a].push_back(b);
		adj[b].push_back(a);
	}
	for (int i = 1; i <= n; i++) cin >> ok[i];
	int x = min(ans(1, -1, 0, 0), ans(1, -1, 0, 1));
	if (x <= n) {
		cout << x << '\n';
	} else {
		cout << "impossible\n";
	}
}

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