Submission #2170446

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Source Code Expand

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<algorithm>
#include<map>
#include<set>
#include<queue>
#define fo(i,j,k) for(int i=j;i<=k;++i)
#define fd(i,j,k) for(int i=j;i>=k;--i)
using namespace std;
const int N=1e5+10;
typedef pair<int,int> pr;
map<pr,int> mp;
multiset<int> b[N];
queue<pr> q;
typedef multiset<int>::iterator it;
int f[N];
int find(int x){
	return !f[x]?x:f[x]=find(f[x]);
}
void link(int x,int y){
	b[x].insert(y),b[y].insert(x);
}
pr mkpr(int x,int y){
	if(x>y) swap(x,y);
	return make_pair(x,y);
}
int main()
{
	int n;
	scanf("%d",&n);
	fo(i,1,n*2-2){
		int x,y;
		scanf("%d %d",&x,&y);
		link(x,y);
		pr t=mkpr(x,y);
		++mp[t];
		if(mp[t]==2) q.push(t);
		if(mp[t]>2) return printf("NO"),0;
	}
	fo(ch,2,n){
		if(q.empty()) return printf("NO"),0;
		int x=0,y=0;
		for(;x==y;x=find(q.front().first),y=find(q.front().second),q.pop());
		if(b[x].size()>b[y].size()) swap(x,y);
		f[x]=y;
		for(it i=b[x].begin();i!=b[x].end();i++){
			int v=find(*i);
			b[v].erase(b[v].find(x));
			if(v==y) continue;
			link(v,y);
			pr t=mkpr(v,y);
			++mp[t];
			if(mp[t]==2) q.push(t);
		}
		b[x].clear();
	}
	printf("YES");
}

Submission Info

Compile Error

./Main.cpp: In function ‘int main()’:
./Main.cpp:31:16: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d",&n);
                ^
./Main.cpp:34:23: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d %d",&x,&y);
                       ^

Judge Result