CCF201812-4 数据中心 Kruskal最小生成树

板子题，要注意的是数据范围

acode：
 

#include <bits/stdc++.h>
#define max(x, y) (x > y ? x : y)
#define MAX 500001
using namespace std;
int n, m, ans;
struct node
{
	int start, end, power;//start为起始点，end为终止点，power为权值
} edge[MAX];
int pre[MAX];

int cmp(node a, node b)
{
	return a.power < b.power;//按照权值排序
}

int find(int x)//并查集找祖先
{
	if (x != pre[x])
	{
		pre[x] = find(pre[x]);
	}
	return pre[x];
}

void merge(int x, int y, int n)//并查集合并函数，n是用来记录最短路中应该加入哪个点
{
	int fx = find(x);
	int fy = find(y);
	if (fx != fy)
	{
		pre[fx] = fy;
		ans = max(ans, edge[n].power);
	}
}

int main()
{
	int root;
	cin >> n >> m >> root;
	ans = 0;
	int i;
	int start, end, power;
	for (i = 1; i <= m; i++)
	{
		cin >> start >> end >> power;
		edge[i].start = start, edge[i].end = end, edge[i].power = power;
	}
	for (i = 1; i <= m; i++)
	{
		pre[i] = i;
	}//并查集初始化
	sort(edge + 1, edge + m + 1, cmp);
	for (i = 1; i <= m; i++)
	{
		merge(edge[i].start, edge[i].end, i);
	}
	cout << ans << endl;
	return 0;
}