Submission #1128480

#	Time	Username	Problem	Language	Result	Execution time	Memory
1128480		Alihan_8	The Xana coup (BOI21_xanadu)	C++20	0 / 100	1096 ms	6584 KiB

xanadu

#include <bits/stdc++.h>

using namespace std;

signed main(){
	int n; cin >> n;
	
	vector <vector<int>> adj(n);
	
	for ( int i = 1; i < n; i++ ){
		int u, v; cin >> u >> v;
		
		--u, --v;
		
		adj[u].push_back(v);
		adj[v].push_back(u);
	}
	
	vector <int> a(n);
	
	for ( auto &u: a ) cin >> u;
	
	int opt = n + 1;
	
	for ( int mask = 0; mask < (1 << n); mask++ ){
		vector <int> b = a;
		
		for ( int i = 0; i < n; i++ ){
			if ( mask >> i & 1 ){
				b[i] ^= 1;
				
				for ( auto &v: adj[i] ) b[v] ^= 1;
			}
		}
		
		int mx = 0;
		
		for ( auto &v: b ) mx = max(mx, v);
		
		if ( mx == 0 ){
			int sz = __builtin_popcount(mask);
			
			if ( opt != n + 1 ) assert(false);
			
			opt = sz;
		}
	}
	
	if ( opt == n + 1 ) return cout << "impossible\n", 0;
	
	cout << opt << '\n';
}

• Subtask 1: 0 / 5
• Subtask 2: 0 / 15
• Subtask 3: 0 / 10
• Subtask 4: 0 / 40
• Subtask 5: 0 / 30