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 JAVA (judge verdict: Accepted)

import java.util.*;
import java.io.*;

class Main{
	public static void main(String[] args) throws Exception{
		MyScanner scan = new MyScanner(System.in);
		int v = scan.nextInt();
		int e = scan.nextInt();
		Group[] groups = new Group[v];
		for(int i = 0; i < v; i++) groups[i] = new Group();
		List<Branch> branches = new ArrayList<>(e);
		for(int i = 0; i < e; i++) {
			branches.add(new Branch(
				scan.nextInt(),
				scan.nextInt(),
				scan.nextInt()
			));
		}
		Collections.sort(branches);
		int result = 0;
		for(Branch _b : branches) {
			Group g1 = groups[_b.s].getGroup();
			Group g2 = groups[_b.t].getGroup();
			if(g1==g2) continue;
			Group newg = new Group();
			g1.parent = newg;
			g2.parent = newg;
			result += _b.v;
		}
		System.out.println(result);
	}
}

class Group{
	Group parent;
	Group(){
	}
	Group getGroup() {
		return (parent==null)?this:parent.getGroup();
	}
}

class Branch implements Comparable<Branch>{
	int s,t;
	int v;
	Branch(int _s, int _t, int _v) {
		s = _s;
		t = _t;
		v = _v;
	}
	@Override
	public int compareTo(Branch _b) {
		return this.v - _b.v;
	}
}

class MyScanner{
	InputStream in;
	MyScanner(InputStream _in) {
		in = _in;
	}
	int nextInt() {
		int result = 0;
try{
		int _i = in.read();
		while(_i<'0'||_i>'9') {
			_i = in.read();
		}
		while(_i>='0'&&_i<='9') {
			result *= 10;
			result += (int)(_i-'0');
			_i = in.read();
		}
		return result;
}catch(Exception e) {
	e.printStackTrace();
	return 0;
}
	}
}