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 System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;

namespace A {
	class main {
		public main() { }
		public static int Main() {
			new main().run();
			return 0;
		}
		public struct edge {
			public int from,to,cost;
			public edge(int u, int v, int c) {
				from=u;
				to=v;
				cost=c;
			}
		}
		int[] par = new int[10001];
		int[] rank = new int[10001];
		void init(int n) {
			for(int i=0; i<n; i++){
				par[i]=i;
				rank[i]=0;
			}
		}
		int find(int x) {
			if(par[x]==x) {
				return x;
			} else {
				return par [x] = find (par [x]);
			}
		}
		void unite(int x,int y) {
			x=find(x);
			y=find(y);
			if(x==y) return;
			if(rank[x]<rank[y]) {
				par[x]=y;
			} else {
				par[y]=x;
				if (rank [x] == rank [y])
					rank [x]++;
			}
		}
		bool same(int x,int y) {
			return find (x) == find (y);
		}
		int comp(edge e1, edge e2) {
			if (e1.cost < e2.cost) return -1;
			else return 1;
		}
		int V,E;
		int kruskal(edge[] es) {
			Array.Sort (es, comp);
			init (V);
			int res=0;
			for(int i=0; i<E; i++) {
				edge e = es [i];
				if(!same(e.from,e.to)) {
					unite (e.from, e.to);
					res+=e.cost;
				}
			}
			return res;
		}
		void run() {
			Scanner cin = new Scanner();
			V = cin.nextInt ();
			E = cin.nextInt ();
			edge[] es = new edge[E];
			for (int i = 0; i < E; i++) {
				es[i].from = cin.nextInt ();
				es[i].to = cin.nextInt ();
				es[i].cost = cin.nextInt ();
			}
			Console.WriteLine("{0}",kruskal(es)); 
		}
	}

	class Scanner {
		string[] s;
		int i;

		char[] cs = new char[] { ' ' };

		public Scanner() {
			s = new string[0];
			i = 0;
		}
		public string next() {
			if (i < s.Length) return s[i++];
			s = Console.ReadLine().Split(cs, StringSplitOptions.RemoveEmptyEntries);
			i = 0;
			return s[i++];
		}
		public int nextInt() {
			return int.Parse(next());
		}
		public long nextLong() {
			return long.Parse(next());
		}
		public double nextDouble() {
			return double.Parse(next());
		}
	}
}