Submission #2162263

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Source Code Expand

#include <bits/stdc++.h>

#define FOR(i,a,b) for(i=(a);i<(b);i++)
#define REP(i,a) FOR(i,0,a)

using namespace std;
typedef pair<int,bool> P;

const int MAX_N=1e5;

set<P> G[MAX_N];

int main(){
	int N;
	int i;
	scanf("%d",&N);
	REP(i,N-1){
		int a,b;
		scanf("%d %d",&a,&b);
		a--;
		b--;
		G[a].insert(P(b,false));
		G[b].insert(P(a,false));
	}
	REP(i,N-1){
		int a,b;
		scanf("%d %d",&a,&b);
		a--;
		b--;
		G[a].insert(P(b,true));
		G[b].insert(P(a,true));
	}
	int c=0;
	REP(i,N){
		int v=i,v2;
		while(1){
			v2=-1;
			for(auto ite=G[v].begin();ite!=G[v].end();){
				auto ite2=ite;
				ite2++;
				if (ite2==G[v].end()) break;
				if (ite->first==ite2->first){
					v2=ite->first;
					if (G[v].size()<G[v2].size()){
						swap(v,v2);
					}
					break;
				}
				ite++;
				if (ite->second){
					ite++;
				}
			}
			if (v2!=-1){
				c++;
				G[v].erase(P(v2,false));
				G[v].erase(P(v2,true));
				G[v2].erase(P(v,false));
				G[v2].erase(P(v,true));
				for(auto ite2=G[v2].begin();ite2!=G[v2].end();){
					G[ite2->first].erase(P(v2,ite2->second));
					G[ite2->first].insert(P(v,ite2->second));
					G[v].insert(*ite2);
					ite2=G[v2].erase(ite2);
				}
			}else{
				break;
			}
		}
	}
	if (c==N-1){
		printf("YES\n");
	}else{
		printf("NO\n");
	}
	return 0;
}

Submission Info

Compile Error

./Main.cpp: In function ‘int main()’:
./Main.cpp:16:16: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d",&N);
                ^
./Main.cpp:19:23: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d %d",&a,&b);
                       ^
./Main.cpp:27:23: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d %d",&a,&b);
                       ^

Judge Result