#include <bits/stdc++.h>
#define fi first
#define se second
#define pb push_back
#define fio ios::sync_with_stdio(false);cin.tie(0);
#define pii pair<int,int>
#define vi vector<int>
#define vc vector<char>
#define pi 3.1415926
#define ls l,m,rt<<1
#define rs m+1,r,rt<<1|1const int INF=0x3f3f3f3f;
const int N=2e5+5;typedef long long ll;
typedef double db;
typedef unsigned long long ull;
using namespace std;int n,m;
int pre[N];struct edge
{int start;int to;int value;
}edges[N];void InitPre()//初始化pre数组
{for (int i=1;i<=n;i++){pre[i]=i;}
}int findRoot(int n)//查找根节点
{int r=n;while(pre[r]!=r)//查找这个点的根节点
    {r=pre[r];}//r现在是根节点int i=n,j;while(i!=r)//路径压缩，让小弟直接归老大直辖
    {j=pre[i];pre[i]=r;i=j;}return r;
}void join(int x,int y)//把各个连同分支连起来
{int r1=findRoot(x);int r2=findRoot(y);if(r1!=r2)//如果已经连通不用管
    {pre[r1]=r2;//不连通的时候随便指定一个是另一个的老大
    }
}bool cmp(edge a,edge b)
{return a.value<=b.value;
}void kruskal()
{int sumValue=0;//生成树的权值int cnt=0;//已用边的数量int start,to,value;for (int i=1;i<=m;i++){start=edges[i].start;to=edges[i].to;if(findRoot(start)!=findRoot(to)){cout<<start<<"---"<<to<<" "<<edges[i].value<<endl;sumValue+=edges[i].value;cnt++;join(start,to);}if(cnt>=n-1) break;}cout<<"SumValue: "<<sumValue<<endl;
}int main()
{//n个点m条边cin>>n>>m;InitPre();for (int i=1;i<=m;i++){cin>>edges[i].start>>edges[i].to>>edges[i].value;}sort(edges+1,edges+1+m,cmp);cout<<endl<<endl;kruskal();
}

7 9
1 2 28
1 6 10
2 3 16
2 7 14
3 4 12
4 5 22
4 7 18
5 6 25
5 7 24

 1 #include <bits/stdc++.h>
 2 #define fi first
 3 #define se second
 4 #define pb push_back
 5 #define fio ios::sync_with_stdio(false);cin.tie(0);
 6 #define pii pair<int,int>
 7 #define vi vector<int>
 8 #define vc vector<char>
 9 #define pi 3.1415926
10 #define ls l,m,rt<<1
11 #define rs m+1,r,rt<<1|1
12
13 const int INF=0x3f3f3f3f;
14 const int N=2e5+5;
15
16 typedef long long ll;
17 typedef double db;
18 typedef unsigned long long ull;
19 using namespace std;
20 struct Edge
21 {
22     int u,v,w;
23 }edge[200005];
24
25 int fa[5005],n,m,ans,eu,ev,cnt;
26 inline bool cmp(Edge a,Edge b)
27 {
28      return a.w<b.w;
29 }//快排的依据
30 inline int findRoot(int x){
31     while(x!=fa[x]) x=fa[x]=fa[fa[x]];
32     return x;
33 }
34 inline void kruskal(){
35     sort(edge,edge+m,cmp);//将边的权值排序
36     for(int i=0;i<m;i++){
37         eu=find(edge[i].u), ev=find(edge[i].v);
38         if(eu==ev) continue;//若出现环，则continue
39         ans+=edge[i].w;//更新答案
40         fa[ev]=eu; cnt++;
41         if(cnt==n-1) break;//循环结束条件
42     }
43 }
44 int main(){
45     scanf("%d%d",&n,&m);
46     for(int i=1;i<=n;i++) fa[i]=i;//初始化并查集
47     for(int i=0;i<m;i++)
48         scanf("%d%d%d",&edge[i].u,&edge[i].v,&edge[i].w);
49     kruskal();
50     printf("%d",ans);
51     return 0;
52 }