MLE代码：

#include<iostream>
#include<cstdio>
#include<queue>
#include<vector>
#include<algorithm>
//#include<cstring>
#include<string>
#include<iomanip>
#include<cmath>
#include<stack>
#include<map>
using namespace std;
typedef long long ll;
const int M = 2e4 + 5;
int fa[M];
int find(int x)
{
	return x == fa[x]? x : (fa[x] = find(fa[x]));
}
int di[M];
ll n, m, u, v, w;
struct node { int u, v, w; };

bool cmp(node a, node b)
{
	return a.w > b.w;
}
node fan[100005];
int main() {
	
	cin >> n >> m;
	for (int i = 1; i <= n; i++)
		fa[i] = i;
	for (int i = 1; i <= m; i++)
	{
		cin >> fan[i].u >> fan[i].v >> fan[i].w;
	}
	sort(fan + 1, fan + m + 1,cmp);
	for (int i = 1; i <= m; i++)
	{
		if (find(fan[i].u) == find(fan[i].v)) { cout << fan[i].w; exit(0); }
		if (!di[fan[i].u]) di[fan[i].u] = find(fan[i].v);
		else fa[find(di[fan[i].u])] = fan[i].v;
		if (!di[fan[i].v]) di[fan[i].v] = find(fan[i].u);
		else fa[find(di[fan[i].v])] = fan[i].u;
	}
	cout << 0;
}

AC代码：

#include<iostream>
#include<cstdio>
#include<queue>
#include<vector>
#include<algorithm>
//#include<cstring>
#include<string>
#include<iomanip>
#include<cmath>
#include<stack>
#include<map>
using namespace std;
typedef long long ll;
const int M = 2e4 + 5;
int fa[M];
int find(int x)
{
	return x == fa[x]? x : (fa[x] = find(fa[x]));
}
int di[M];
ll n, m, u, v, w;
struct node { int u, v, w; };

bool cmp(node a, node b)
{
	return a.w > b.w;
}
node fan[100005];
int main() {
	
	cin >> n >> m;
	for (int i = 1; i <= n; i++)
		fa[i] = i;
	for (int i = 1; i <= m; i++)
	{
		cin >> fan[i].u >> fan[i].v >> fan[i].w;
	}
	sort(fan + 1, fan + m + 1,cmp);
	for (int i = 1; i <= m; i++)
	{
		if (find(fan[i].u) == find(fan[i].v)) { cout << fan[i].w; exit(0); }
		if (!di[fan[i].u]) di[fan[i].u] = find(fan[i].v);
		else fa[find(di[fan[i].u])] = find(fan[i].v);
		if (!di[fan[i].v]) di[fan[i].v] = find(fan[i].u);
		else fa[find(di[fan[i].v])] = find(fan[i].u);
	}
	cout << 0;
}