Submission #1370452

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Source Code Expand

#include <bits/stdc++.h>

using namespace std;

#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()
#define fi first
#define se second

template<typename A, typename B> inline bool chmax(A &a, B b) { if (a<b) { a=b; return 1; } return 0; }
template<typename A, typename B> inline bool chmin(A &a, B b) { if (a>b) { a=b; return 1; } return 0; }

typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<int, pll> P;

const ll INF = 1ll<<30;
const ll MOD = 1000000007;
const double EPS  = 1e-10;

int N;
int a[112345];
vector<int> g[112345];
vector<pll> buf[112345];

int main() {
	cin >> N;
	REP(i, N) scanf("%d", a + i);
	REP(i, N - 1) {
		int a, b;
		scanf("%d %d", &a, &b);
		a--; b--;
		g[a].push_back(b);
		g[b].push_back(a);
	}
	
	
	queue<pii> que; // 現在の頂点, どの頂点からきたか
	
	bool ans = true;
	
	if (N == 2 && a[0] != a[1]) ans = false;
	
	while (!que.empty()) {
		pii now = que.front(); que.pop();
		
		int u = now.fi, bef = now.se;
		ll sum = 0, cnt = 0;
		REP(i, buf[u].size()) {
			sum += buf[u][i].fi;
			if (buf[u][i].se != -1) cnt++;
		}
		
		if (cnt + 1 == g[u].size()) {
			ll to = 2 * a[u] - sum;
			if (to < 0) ans = false;
			
			set<int> ss;
			REP(i, buf[u].size()) ss.insert(buf[u][i].se);
			REP(i, g[u].size()) {
				int v = g[u][i];
				if (v == bef || ss.find(u) != ss.end()) continue;
				
				que.push(pii(v, u));
				buf[v].push_back(pll(to, u));
			}
		}
		else if (cnt == g[u].size()) {
			if (sum != 2 * a[u]) ans = false;
		}
	}
	
	puts(ans ? "YES" : "NO");
	
	return 0;
}

Submission Info

Compile Error

./Main.cpp: In function ‘int main()’:
./Main.cpp:30:30: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
  REP(i, N) scanf("%d", a + i);
                              ^
./Main.cpp:33:25: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d %d", &a, &b);
                         ^

Judge Result