Submission #526024

#	Time	Username	Problem	Language	Result	Execution time	Memory
526024		Gurban	The Xana coup (BOI21_xanadu)	C++17	10 / 100	46 ms	15556 KiB

xanadu

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

using ll = long long;

const int maxn=1e5+5;
int n;
int dp[maxn][2][2];
int col[maxn];
vector<int>E[maxn];

void dfs(int nd,int pr){
	if(!col[nd]){
		dp[nd][0][0] = 0;
		dp[nd][0][1] = 1e9;
		dp[nd][1][0] = 1e9;
		dp[nd][1][1] = 1;
	}
	else {
		dp[nd][1][0] = 0;
		dp[nd][1][1] = 1e9;
		dp[nd][0][0] = 1e9;
		dp[nd][0][1] = 1;
	}

	int now[2][2];
	for(int i = 0;i < 2;i++) for(int j = 0;j < 2;j++) now[i][j] = 0;
	for(auto i : E[nd]) if(i != pr){
		dfs(i,nd);
		now[0][0] = min(dp[nd][0][0] + dp[i][0][0],dp[nd][1][0] + dp[i][0][1]);
		now[0][1] = min(dp[nd][0][1] + dp[i][1][0],dp[nd][1][1] + dp[i][1][1]);
		now[1][0] = min(dp[nd][0][0] + dp[i][0][1],dp[nd][1][0] + dp[i][0][0]);
		now[1][1] = min(dp[nd][0][1] + dp[i][1][1],dp[nd][1][1] + dp[i][1][0]);
		
		for(int j = 0;j < 2;j++) for(int k = 0;k < 2;k++) dp[nd][j][k] = now[j][k];
	}
}

int main(){
	ios::sync_with_stdio(false);
	cin.tie(0);

	cin >> n;
	for(int i = 1;i <= n;i++) for(int j = 0;j < 2;j++) for(int k = 0;k < 2;k++) dp[i][j][k] = 1e9;
	for(int i = 1;i < n;i++){
		int x,y; cin >> x >> y;
		E[x].push_back(y);
		E[y].push_back(x);
	}
	for(int i = 1;i <= n;i++) cin >> col[i];
	dfs(1,0);
	int ans = min(dp[1][0][0],dp[1][0][1]);
	if(ans >= 1e9) cout<<"impossible";
	else cout<<ans;
}

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