Submission #1370388

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Source Code Expand

#include <iostream>
#include <vector>
using namespace std;

int main(){
	int n,a[100000],sum = 0;
	vector<int> G[100000];
	bool flag = true;
	cin >> n;
	for(int i = 0;i < n;i++) cin >> a[i];
	for(int i = 0;i < n - 1;i++){
		int u,v;
		cin >> u >> v; u--;v--;
		G[u].push_back(v);
		G[v].push_back(u);
	}
	for(int i = 0;i < n;i++){
		int cnt = 0;
		for(int j = 0;j < G[i].size();j++) cnt += a[G[i][j]];
		if(G[i].size() == 1) sum += a[i];
		if(G[i].size() == 1 && cnt < a[i]) flag = false;
		if(G[i].size() >= 2 && cnt < a[i] * 2) flag = false;
	}
	if(sum % 2) flag = false;
	if(flag) cout << "YES" << endl;
	else cout << "NO" << endl;
	return 0;
}

Submission Info

Judge Result