程式碼如下

#include <bits/stdc++.h>
using namespace std;
const int maxv=2e5+10;
const int maxe=5e5+10;

inline int read(){
    int x=0,f=1;char ch;
    do{ch=getchar();if(ch=='-')f=-1;}while(!isdigit(ch));
    do{x=x*10+ch-'0';ch=getchar();}while(isdigit(ch));
    return f*x;
}

struct node{int from,to,w;}e[maxe];
int n,m,sum,f[maxv];
long long ans;

bool cmp(const node& x,const node& y){return x.w<y.w;}

int find(int x){return x==f[x]?x:f[x]=find(f[x]);}

void read_and_parse(){
    n=read(),m=read();
    for(int i=1;i<=n;i++)f[i]=i;
    for(int i=1;i<=m;i++)scanf("%d%d%d",&e[i].from,&e[i].to,&e[i].w);
}

void solve(){
    sort(e+1,e+m+1,cmp);
    for(int i=1;i<=m;i++){
        if(sum==n-1)break;
        int x=find(e[i].from),y=find(e[i].to);
        if(x^y)f[x]=y,ans+=e[i].w,++sum;
    }
    printf("%lld\n",ans);   
}

int main(){
    read_and_parse();
    solve();
    return 0;
}