USACO 3.2 butter 最短路

堆优化dijkstra

 /*
 PROB:butter
 LANG:C++
 */

 #include <iostream>
 #include <cstdio>
 #include <queue>
 #include <vector>
 using namespace std;
 const int Ni = ;
 const int INF = <<;
 struct node{
     int x,d;
     node(){}
     node(int a,int b){x=a;d=b;}
     bool operator < (const node & a) const
     {
         if(d==a.d) return x<a.x;
         else return d > a.d;
     }
 };
 vector<node> eg[Ni];
 int dis[Ni],cow[Ni],ans,p,c,n;

 void Dijkstra(int s)
 {
     int i;
     for(i=;i<=p;i++) dis[i]=INF;
     dis[s]=;
     priority_queue<node> q;
     q.push(node(s,dis[s]));
     while(!q.empty())
     {
         node x=q.top();q.pop();
         for(i=;i<eg[x.x].size();i++)
         {
             node y=eg[x.x][i];
             if(dis[y.x]>x.d+y.d)
             {
                 dis[y.x]=x.d+y.d;
                 q.push(node(y.x,dis[y.x]));
             }
         }
     }
 }
 int main()
 {
     freopen("butter.in","r",stdin);
     freopen("butter.out","w",stdout);

     ans=INF;
     scanf("%d %d %d",&n,&p,&c);
     for (int i=;i<=n;i++)
         scanf("%d",&cow[i]);
     for (int i=;i<=c;i++)
     {
         int x,y,t;
         scanf("%d %d %d",&x,&y,&t);
         //a[x][y]=t;        a[y][x]=t;
         eg[x].push_back(node(y,t));
         eg[y].push_back(node(x,t));
     }

     for (int k=;k<=p;k++)
     {
         Dijkstra(k);

         int tmp=;
         for (int i=;i<=n;i++)
             tmp+=dis[cow[i]];
         if (tmp<ans)
             ans=tmp;
     }
     printf("%d\n",ans);

     return ;
 }