Minimum Spanning Tree SPOJ - MST

题目：Minimum Spanning Tree SPOJ - MST 

题意：n个结点，m条边，然后依次给出这m条边的首结点，尾结点，及边长。求连接所有结点的边长最小和为多少。

思路：基本的最小生成树问题，用Kruskal算法解决（注意，结果要用long long储存，不然会gg）

#define _CRT_SECURE_NO_WARNINGS
#include<iostream>
#include<cstdio>
#include<math.h>
#include<vector>
#include<string>
#include<map>
#include<queue>
#include<algorithm>
#include<string.h>
using namespace std;
/*最小生成树*/

int node_check[10086];
struct my_node
{
	int first_node;
	int end_node;
	int weight;
};
bool cmp(my_node a,my_node b)
{
	if (a.weight<b.weight)
	{
		return true;
	}
	else
	{
		return false;
	}
}

int tree_find(int x)
{
	if (node_check[x]==x)
	{
		return x;
	}
	else
	{
		return tree_find(node_check[x]);
	}
}

int main()
{
	for (int i = 0; i < 10086; i++)
	{
		node_check[i] = i;
	}
	int node, edge;
	cin >> node >> edge;
	vector<my_node>test;
	for (int  i = 0; i < edge; i++)
	{
		my_node temp;
		cin >> temp.first_node >> temp.end_node >> temp.weight;
		test.push_back(temp);
	}
	sort(test.begin(),test.end(), cmp);
	long long  my_result = 0;
	int flag = 0;
	for (int  i = 0; i < edge; i++)
	{
		int first_root = tree_find(node_check[test[i].first_node]);
		int end_root = tree_find(node_check[test[i].end_node]);
		if (first_root!=end_root)
		{
			my_result += test[i].weight;
			flag++;
			node_check[end_root] = node_check[first_root];
			if (flag == (node - 1))
			{
				break;
			}
		}
	}
	cout << my_result << endl;
}