Prim's Algorithm

#include<iostream>
#include<vector>
#include<queue>
#include<fstream>
#include<set>
#include<cstring>
#include<algorithm>
using namespace std;
#define Max 100
#define pb push_back
#define READ(f) freopen(f, "r", stdin)
#define WRITE(f) freopen(f, "w", stdout)
#define G struct prims

G
{
    int u,v,cost;
    bool operator < (const G& a) const{
        return cost>a.cost;
    }
}p[Max];
priority_queue<G>q,q1,x;
int visited[Max+1];
int main()
{
    READ("in.txt");
    memset(visited,0,sizeof(visited));
    int num_edge,sum=0,src;
    cin>>num_edge;
    for(int i=1;i<=num_edge;i++)
    {
        cin>>p[i].u>>p[i].v>>p[i].cost;
        q.push(p[i]);
    }
     cin>>src;
     visited[src]=1;
     while(!q.empty())
     {
         G pop;
         pop=q.top();
         if((visited[pop.u]) || (visited[pop.v]))
         {
              if((visited[pop.u]) && (visited[pop.v]))
              {
                  q.pop();
                  continue;
              }
                   visited[pop.u]=visited[pop.v]=1;
                   sum+=pop.cost;
                   q.pop();

         }
         else
         {
           //q.push(pop);
            //x.push(pop);

         }
     }
    //cout<<sum;
    return 0;
}