多次使用dijkstra就行， 代码如下：

　　

/*    ID: m1500293    LANG: C++    PROG: butter*/#include 
     
      #include 
      
       #include 
       
        #include 
        
         #include 
         
          using namespace std;int N, P, C;           //牛的数量 牧场的数量 边的数量int cows[550];struct edge{    int to, cost;    edge() {}    edge(int to, int cost):to(to), cost(cost) {}};vector
          
            G[810];struct Dij{ int u, cost; Dij() {} Dij(int u, int cost):u(u), cost(cost) {} bool operator<(const Dij &r) const { return cost > r.cost; }};int dist[810], vis[810];void dijkstra(int s){ memset(vis, 0, sizeof(vis)); memset(dist, 0x3f, sizeof(dist)); priority_queue
           
             que; dist[s] = 0; que.push(Dij(s, 0)); while(!que.empty()) { Dij u = que.top(); que.pop(); if(vis[u.u]) continue; vis[u.u] = 1; for(int i=0; i
            
              dist[u.u]+e.cost) { dist[e.to] = dist[u.u]+e.cost; que.push(Dij(e.to, dist[e.to])); } } }}int main(){ freopen("butter.in", "r", stdin); freopen("butter.out", "w", stdout); scanf("%d%d%d", &N, &P, &C); for(int i=0; i