蒟蒻求助 大佬请看

#include<bits/stdc++.h>
using namespace std;
int n,m;
int fa[100005];
struct xx{
	int x,y,t;
}f[100005];
void makeSet(int n)
{
	for(int i=1;i<=n;i++)
	{
		fa[i]=i;
	}
}
bool cmp(xx x,xx y)
{
	return x.t<y.t;
}
int find(int x) {
  if (x != fa[x])  fa[x] = find(fa[x]);  
  return fa[x];
}
void unionSet(int x, int y) {
  x = find(x);
  y = find(y);
  fa[x] = y;  
  return;
}
bool check(int x)
{
	int s=find(x);
	for(int i=1;i<=n;i++)
	{
		if(s!=find(fa[i]))
		{
			return false;
		}
	}
	return true;
}
int main()
{
	int n,m;
	cin>>n>>m;
	makeSet(n);
	for(int i=1;i<=m;i++)
	{
		cin>>f[i].x>>f[i].y>>f[i].t;
	//	if(f[i].x<f[i].y)
//	swap(f[i].x,f[i].y);
		
	}
	sort(f+1,f+1+n,cmp);
	for(int i=1;i<=m;i++)
	{   
	    unionSet(f[i].x,f[i].y);
		if(check(f[i].x))
		{
			cout<<f[i].t;
			return 0;
		}
	}
	cout<<"-1";
	return 0;
}