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)

#include <stdio.h>
#include <stdlib.h>
#define E_MAX 100000
#define V_MAX 10001

typedef struct edge {
    int s, t, w;
} edge;

edge edges[E_MAX];
int x[V_MAX];

int compare(const void *a, const void *b) {
    return (*(edge *)a).w - (*(edge *)b).w;
}

void initx(int n) {
    for(int i=0; i<n; i++) x[i] = i;
}

void unite(int a, int b) {
    x[x[b]] = x[a];
}

int find(int a) {
    if (x[a] == a) return a;
    else return x[a] = find(x[a]);
}

int same(int a, int b) {
    return find(a) == find(b);
}

int main() {
    int n, m, cnt = 0;
    scanf("%d%d", &n, &m);
    initx(n);
    for(int i=0; i<m; i++)
        scanf("%d%d%d", &edges[i].s, &edges[i].t, &edges[i].w);

    qsort(edges, m, sizeof(edge), compare);

    for(int i=0; i<m; i++) {
        edge e = edges[i];
        if (!same(e.s, e.t)) {
            unite(e.s, e.t);
            cnt += e.w;
        }
    }
    printf("%d\n", cnt);
}