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++11 (judge verdict: Accepted)

#include <iostream>
#include <iomanip>
#include <vector>
#include <algorithm>
#include <numeric>
#include <functional>
#include <cmath>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <sstream>
#include <string>

#define repd(i,a,b) for (int i=(a);i<(b);i++)
#define rep(i,n) repd(i,0,n)
#define var auto
#define mod 1000000007
#define inf 2147483647
#define nil -1
typedef long long ll;

using namespace std;

inline int input(){
    int a;
    cin >> a;
    return a;
}

template <typename T>
inline void output(T a, int p) {
    if(p){
        cout << fixed << setprecision(p)  << a << "\n";
    }
    else{
        cout << a << "\n";
    }
}

// end of template

// union find
class union_find {
public:
    vector<int> parent, rnk;
    
    union_find(int n){
        parent.resize(n);
        rnk.resize(n, 0);
        rep(i, n){
            parent[i] = i;
        }
    }
    
    int root(int x){
        if (parent[x] == x) {
            return x;
        }
        else{
            return root(parent[x]);
        }
    }
    
    void unite(int x, int y){
        x = root(x);
        y = root(y);
        if (x == y) {
            return;
        }
        if (rnk[x] < rnk[y]) {
            parent[x] = y;
        }
        else{
            parent[y] = x;
            if (rnk[x] == rnk[y]) {
                rnk[x]++;
            }
        }
    }
    
    bool same(int x, int y){
        return root(x) == root(y);
    }
};

struct edge{
    int f, t, cost;
    // define e1.cost < e2.cost : e1 < e2
    bool operator < (const edge &e){
        return cost < e.cost;
    }
};

class kruskal{
public:
    int v; // vertices
    vector<edge> e; // edges
    
    kruskal(int vt, int eg){
        v = vt;
        e.resize(eg);
    }
    
    int mst(){
        sort(e.begin(), e.end());
        union_find uf(v);
        int min_cost = 0;
        rep(i, e.size()){
            edge &d = e[i];
            if (!uf.same(d.f, d.t)) {
                min_cost += d.cost;
                uf.unite(d.f, d.t);
            }
        }
        
        return min_cost;
    }
};


int main() {
    cin.tie(0);
    // source code
    int V, E;
    cin >> V >> E;
    kruskal ks(V, E);
    rep(i, E){
        int s, t, c;
        cin >> s >> t >> c;
        ks.e[i] = edge{s, t, c};
    }
    
    cout << ks.mst() << endl;
    
    
    return 0;
}