【模板】MST（Prim）

代码如下

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

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 nxt,to,w;
}e[maxe<<1];
int tot=1,head[maxv];
inline void add_edge(int from,int to,int w){
	e[++tot]=node{head[from],to,w},head[from]=tot;
}
int n,m,d[maxv];
bool vis[maxv];
long long ans;
priority_queue<P> q;

void read_and_parse(){
	n=read(),m=read();
	for(int i=1;i<=m;i++){
		int from=read(),to=read(),w=read();
		add_edge(from,to,w),add_edge(to,from,w);
	}
}

void solve(){
	memset(d,0x3f,sizeof(d));
	d[1]=0,q.push(make_pair(0,1));
	while(q.size()){
		int u=q.top().second,cost=q.top().first*-1;q.pop();
		if(vis[u])continue;
		vis[u]=1,ans+=cost;
		for(int i=head[u];i;i=e[i].nxt){
			int v=e[i].to,w=e[i].w;
			if(!vis[v]&&w<d[v]){
				d[v]=w;
				q.push(make_pair(-d[v],v));
			}
		}
	}
	printf("%lld\n",ans);
}

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