pta 编程题20 旅游规划

其它pta数据结构编程题请参见：pta

题目

这个最短路径问题只需要求两点之间的最短路径，因而在Dijikstra算法中当求出目标点的最短路径之后跳出循环即可。

 #include <iostream>
 using namespace std;

 struct Node
 {
     int length;
     int price;
 };

 int V, E;
 Node **G;

 void buildGraph();
 void deleteGraph();
 void dijkstra(int s, int d);
 int findMinDist(Node* dist, bool* collected);
 bool cmp(Node a, Node b);

 int main()
 {
     int S, D;
     cin >> V >> E >> S >> D;
     buildGraph();
     dijkstra(S, D);
     deleteGraph();
     return ;
 }

 void buildGraph()
 {
     int a, b, l, p, i;
     G = new Node*[V];
     for (a = ; a < V; a++)
     {
         G[a] = new Node[V];
         for (b = ; b < V; b++)
         {
             G[a][b].length = INT_MAX;
             G[a][b].price = INT_MAX;
         }
     }

     for (i = ; i < E; i++)
     {
         cin >> a >> b >> l >> p;
         G[a][b].length = l;
         G[a][b].price = p;
         G[b][a].length = l;
         G[b][a].price = p;
     }
 }

 void deleteGraph()
 {
     for (int i = ; i < V; i++)
         delete[] G[i];
     delete[] G;
 }

 bool cmp(Node a, Node b)
 {
     if (a.length != b.length)
         return a.length < b.length;
     else
         return a.price < b.price;
 }

 int findMinDist(Node* dist, bool* collected)
 {
     int minV;
     Node minDist;
     minDist.length = INT_MAX;
     minDist.price = INT_MAX;

     for (int i = ; i < V; i++)
     {
         if (!collected[i] && cmp(dist[i], minDist))
         {
             minDist = dist[i];
             minV = i;
         }
     }

     if (minDist.length == INT_MAX)
         return -;
     else
         return minV;
 }

 void dijkstra(int s, int d)
 {
     int v, w;
     Node *dist, temp;
     bool *collected;
     dist = new Node[V];
     collected = new bool[V];
     for (v = ; v < V; v++)
     {
         dist[v] = G[s][v];
         collected[v] = false;
     }

     dist[s].length = ;
     dist[s].price = ;
     collected[s] = true;

     while (true)
     {
         v = findMinDist(dist, collected);
         if (v == d) break;
         collected[v] = true;

         for (w = ; w < V; w++)
         {
             if (!collected[w] && G[v][w].length < INT_MAX)
             {
                 temp.length = dist[v].length + G[v][w].length;
                 temp.price = dist[v].price + G[v][w].price;
                 if (cmp(temp, dist[w]))
                     dist[w] = temp;
             }
         }
     }

     cout << dist[d].length << " " << dist[d].price;
     delete dist;
     delete collected;
 }