3.1circle

就是括号匹配的题目，如果有交集就是NO

#include<iostream> 
#include<cstring>
#include<stdio.h>
#include<stack>
#include<algorithm> 
using namespace std;
stack<int> s;
int a[200005];
int main()
{
	int t,n,m,temp1,temp2,i;
	scanf("%d",&t);
	while(t--)
	{
		int n,m;
		scanf("%d%d",&n,&m);
		memset(a,0,sizeof (a));
		while(!s.empty()) s.pop();
		for(i=1;i<=m;i++)
		{
			scanf("%d%d",&temp1,&temp2);
		    a[temp1]=i;a[temp2]=i;
		}
		for(i=1;i<=2*n;i++)
		{
			if(a[i]==0) continue;
			if(s.empty()) s.push(a[i]);
			else
			{
				if(a[i]==s.top()) s.pop(); 
				else s.push(a[i]);
			}
		}
		if(s.empty()) printf("YES
");
		else printf("NO
");
	}
	
}