prim队列优化

#include<stdio.h>    //大概要这些头文件
#include<string.h>
#include<queue>
#include<vector>
#include<algorithm>
using namespace std;
typedef pair<int,int> pii;

int head[30],next[200],point[200],val[200],size,dist[30];    //前向星及dist数组
bool vis[30];

void add (int a,int b, int v){    //加边及去重
    int i;
    for(i=head[a];~i;i=next[i]){
        if(point[i]==b){
            if(val[i]>v)val[i]=v;
            return;
        }    
    }
    point[size]=b;
    val[size]=v;
    next[size]=head[a];
    head[a]=size++;
}

struct cmp{    //重载小根堆
    bool operator()(pii a,pii b){
        return a.first>b.first;
    }
};

void prim(int s){    //prim函数，传入图中一点
    int i,ans=0;
    memset(dist,-1,sizeof(dist));
    memset(vis,0,sizeof(vis));
    priority_queue<pii,vector<pii>,cmp>q;
    for (i=head[s];~i;i=next[i]){
        dist[point[i]]=val[i];
        q.push(make_pair(dist[point[i]],point[i]));
    }
    dist[s]=0;
    vis[s]=1;
    while(!q.empty()){
        pii u=q.top();
        q.pop();
        if(vis[u.second])continue;
        vis[u.second]=1;
        ans+=u.first;
        for(i=head[u.second];~i;i=next[i]){
            int j=point[i];
            if(!vis[j]&&(dist[j]>val[i]||dist[j]==-1)){
                dist[j]=val[i];
                q.push(make_pair(dist[j],j));
            }
        }
    }
    printf("%d\n",ans);
}