1 //克鲁斯卡尔
2 #include <iostream>
3 #include <algorithm>
4
5 using namespace std;
6 const int maxn = 50000 + 5;
7
8 struct node{
9 int x, y;
10 int len;
11 }g[maxn];
12
13 bool cmp(node x, node y){
14 return x.len < y.len;
15 }
16
17 int fa[maxn];
18
19 int Find(int x){
20 if (x == fa[x])
21 return x;
22 else
23 return fa[x] = Find(fa[x]);
24 }
25
26
27 int main(){
28 ios::sync_with_stdio(false);
29
30 int n, m;
31 cin >> n >> m;
32 for (int i = 0; i <= n; i++){
33 fa[i] = i;
34 }
35
36 int a, b, c;
37 for (int i = 0; i < m; i++){
38 cin >> a >> b >> c;
39 g[i].x = a;
40 g[i].y = b;
41 g[i].len = c;
42 }
43 int ans = 0;
44 sort(g, g + m, cmp);
45 for (int i = 0; i < m; i++){
46 int u, v;
47 u = g[i].x;
48 v = g[i].y;
49 int u1 = Find(u);
50 int v1 = Find(v);
51 if (u1 != v1){
52 fa[v1] = u1;
53 ans += g[i].len;
54 }
55 }
56 cout << ans << endl;
57 return 0;
58 }
