Problem:
Minimum Spanning Tree

Find the sum of weights of edges of the Minimum Spanning Tree for a given weighted undirected graph G = (V, E).

Input

|V| |E|
s0 t0 w0
s1 t1 w1
:
s|E|-1 t|E|-1 w|E|-1

, where |V| is the number of vertices and |E| is the number of edges in the graph. The graph vertices are named with the numbers 0, 1,..., |V|-1 respectively.

si and ti represent source and target verticess of i-th edge (undirected) and wi represents the weight of the i-th edge.

Output

Print the sum of the weights of the Minimum Spanning Tree.

Constraints

1 ≤ |V| ≤ 10,000

0 ≤ |E| ≤ 100,000

0 ≤ wi ≤ 10,000

The graph is connected

There are no parallel edges

There are no self-loops

Sample Input 1

4 6
0 1 2
1 2 1
2 3 1
3 0 1
0 2 3
1 3 5

Sample Output 1

3

Sample Input 2

6 9
0 1 1
0 2 3
1 2 1
1 3 7
2 4 1
1 4 3
3 4 1
3 5 1
4 5 6

Sample Output 2

5

Solution in C# (judge verdict: Accepted)

using static System.Math;
using static System.Console;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace AOJ
{
    class Program
    {
        static void Main(string[] args)
        {
            var line = ReadLine().Split(' ').Select(value => int.Parse(value)).ToArray();
            var v = line[0];
            var e = line[1];
            var edges = new List<int[]>();
            for (var i = 0; i < e; i++)
            {
                line = ReadLine().Split(' ').Select(value => int.Parse(value)).ToArray();
                edges.Add(line);
            }
            edges = edges.OrderBy(array => array[2]).ToList();
            var parents = new int[v];
            for(var i = 0; i < v; i++)
            {
                parents[i] = i;
            }

            var cost = 0;
            foreach(var edge in edges)
            {
                if(GetRoot(parents, edge[0]) != GetRoot(parents, edge[1]))
                {
                    cost += edge[2];
                    Unite(parents, edge[0], edge[1]);
                }
            }

            WriteLine(cost);
        }

        private static int GetRoot(int[] parents, int node)
        {
            if (parents[node] == node)
            {
                return node;
            }
            return parents[node] = GetRoot(parents, parents[node]);
        }

        private static void Unite(int[] parents, int x, int y)
        {
            x = GetRoot(parents, x);
            y = GetRoot(parents, y);

            if (x == y)
            {
                return;
            }
            parents[x] = y;
        }
    }
}