kruskal板子

#include<iostream>
#include<algorithm>
using namespace std;
typedef long long ll;
const int Max = 1e6 + 5;

struct node
{
   
	int u, v, w;
	node(int a=0, int b=0, int c=0)
	{
   
		u = a, v = b, w = c;
	}
	bool operator <(node& a)
	{
   
		return w < a.w;
	}
};

node lst[Max];
int f[Max];

int find(int n)
{
   
	if (f[n] == n)return n;
	else return f[n] = find(f[n]);
}

void merge(int a, int b)
{
   
	if (find(a) == find(b))return;
	f[find(b)] = find(a);
}

int main()
{
   
	int n, m;cin >> n >> m;
	for (int i = 1;i <= n;i++)f[i] = i;
	for (int i = 1;i <= m;i++)
	{
   
		int a, b, c;cin >> a >> b >> c;
		lst[i] = node(a, b, c);
	}
	sort(lst + 1, lst + 1 + m);
	long long sum = 0;
	for (int i = 1;i <= m;i++)
	{
   
		int a = lst[i].u, b = lst[i].v;
		if (find(a) == find(b))continue;
		sum += lst[i].w;
		merge(a, b);
	}
	cout << sum;
}