Submission #1736055

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Source Code Expand

#include<bits/stdc++.h>
using namespace std;
#define X first
#define Y second

const int maxn=1e5+10;

int n,f[maxn];
set<int> r[maxn],b[maxn];
queue<pair<int,int> > q;

int find(int x) {return x==f[x]?x:f[x]=find(f[x]);}

int main()
{
#ifdef h10
	freopen("E.in","r",stdin);
	freopen("E.out","w",stdout);
#endif
	int i,u,v;
	scanf("%d",&n);
	for (i=1;i<=n;i++) f[i]=i;
	for (i=1;i<n;i++)
	{
		scanf("%d%d",&u,&v);
		r[u].insert(v);
		r[v].insert(u);
	}
	for (i=1;i<n;i++)
	{
		scanf("%d%d",&u,&v);
		b[u].insert(v);
		b[v].insert(u);
		if (r[u].count(v))
			q.push(make_pair(u,v));
	}
	while (!q.empty())
	{
		u=find(q.front().X);
		v=find(q.front().Y);
		q.pop();
		if (u==v) continue;
		if (r[u].size()+b[u].size()<r[v].size()+b[v].size()) swap(u,v);
		set<int>::iterator it;
		for (it=r[v].begin();it!=r[v].end();it++)
		{
			int tmp=find(*it);
			r[u].insert(tmp);
			r[tmp].insert(u);
			if (b[u].count(tmp))
				q.push(make_pair(u,tmp));
		}
		for (it=b[v].begin();it!=b[v].end();it++)
		{
			int tmp=find(*it);
			b[u].insert(tmp);
			b[tmp].insert(u);
			if (r[u].count(tmp))
				q.push(make_pair(u,tmp));
		}
		r[v].clear();
		b[v].clear();
		f[v]=u;
	}
	for (i=2;i<=n;i++)
		if (find(i)!=find(1)) {puts("NO"); return 0;}
	puts("YES");
}

Submission Info

Compile Error

./Main.cpp: In function ‘int main()’:
./Main.cpp:21:16: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d",&n);
                ^
./Main.cpp:25:22: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d",&u,&v);
                      ^
./Main.cpp:31:22: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d",&u,&v);
                      ^

Judge Result