USACO 3.2 butter 最短路

 1 /*
 2 PROB:butter
 3 LANG:C++
 4 */
 5 
 6 #include <iostream>
 7 #include <cstdio>
 8 #include <queue>
 9 #include <vector>
10 using namespace std;
11 const int Ni = 10000;
12 const int INF = 1<<27;
13 struct node{
14     int x,d;
15     node(){}
16     node(int a,int b){x=a;d=b;}
17     bool operator < (const node & a) const
18     {
19         if(d==a.d) return x<a.x;
20         else return d > a.d;
21     }
22 };
23 vector<node> eg[Ni];
24 int dis[Ni],cow[Ni],ans,p,c,n;
25 
26 void Dijkstra(int s)
27 {
28     int i;
29     for(i=0;i<=p;i++) dis[i]=INF;
30     dis[s]=0;
31     priority_queue<node> q;
32     q.push(node(s,dis[s]));
33     while(!q.empty())
34     {
35         node x=q.top();q.pop();
36         for(i=0;i<eg[x.x].size();i++)
37         {
38             node y=eg[x.x][i];
39             if(dis[y.x]>x.d+y.d)
40             {
41                 dis[y.x]=x.d+y.d;
42                 q.push(node(y.x,dis[y.x]));
43             }
44         }
45     }
46 }
47 int main()
48 {
49     freopen("butter.in","r",stdin);
50     freopen("butter.out","w",stdout);
51 
52     ans=INF;
53     scanf("%d %d %d",&n,&p,&c);
54     for (int i=1;i<=n;i++)
55         scanf("%d",&cow[i]);
56     for (int i=1;i<=c;i++)
57     {
58         int x,y,t;
59         scanf("%d %d %d",&x,&y,&t);
60         //a[x][y]=t;        a[y][x]=t;
61         eg[x].push_back(node(y,t));
62         eg[y].push_back(node(x,t));
63     }
64 
65     for (int k=1;k<=p;k++)
66     {
67         Dijkstra(k);
68 
69         int tmp=0;
70         for (int i=1;i<=n;i++)
71             tmp+=dis[cow[i]];
72         if (tmp<ans)
73             ans=tmp;
74     }
75     printf("%d\n",ans);
76 
77     return 0;
78 }