Prim算法——最小生成树

#include <bits/stdc++.h>
using namespace std;

const int maxn=100000+15;
const int maxm=100000+15;
struct Edge
{
    int x,y,z,next;
    Edge(int x=0,int y=0,int z=0,int next=0):x(x),y(y),z(z),next(next) {}
}edge[maxm*2];
const bool operator < (const Edge &a,const Edge &b)
{
    return a.z>b.z;
 } 
int n,m;
int sumedge,head[maxn];
int ins(int x,int y,int z)
{
    edge[++sumedge]=Edge(x,y,z,head[x]);
    return head[x]=sumedge;
}
priority_queue <Edge> que;
int ans;
bool boo[maxn];
int main()
{
    scanf("%d%d",&n,&m);
    for (int i=1;i<=m;i++)
    {
        int x,y,z;
        scanf("%d%d%d",&x,&y,&z);
        ins(x,y,z);
        ins(y,x,z);
    }
    memset(boo,false,sizeof(boo));
    boo[1]=true;
    for (int u=head[1];u;u=edge[u].next) 
      que.push(edge[u]);
    for (int i=1;i<n;i++)    //总共有n-1条边 
    {
        Edge temp;
        temp=que.top();
        for (;boo[temp.y];que.pop(),temp=que.top());
        que.pop();
        ans+=temp.z;
        boo[temp.y]=true;
        for (int u=head[temp.y];u;u=edge[u].next)
         if (!boo[edge[u].y]) que.push(edge[u]);
    }
    printf("%d\n",ans);
    return 0;
 }