pta programming question 16 road to every village

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This question examines the minimum spanning tree problem, using Prim's algorithm.

  1 #include <iostream>
  2 using namespace std;
  3 
  4 int N, M;
  5 int** G;
  6 void buildGraph();
  7 void deleteGraph();
  8 int prim();
  9 int findMinDist(int dist[]);
 10 
 11 int main()
 12 {
 13     cin >> N >> M;
 14     buildGraph();
 15     cout << prim();
 16     deleteGraph();
 17     return 0;
 18 }
 19 
 20 void buildGraph()
 21 {
 22     int i, j;
 23     G = new int*[N];
 24     for (i = 0; i < N; i++)
 25     {
 26         G[i] = new int[N];
 27         for (j = 0; j < N; j++)
 28             G[i][j] = INT_MAX;
 29     }    
 30 
 31     int v, w, d;
 32     for (i = 0; i < M; i++)
 33     {
 34         cin >> v >> w >> d;
 35         v--; w--;//输入从1计数
 36         G[v][w] = d;
 37         G[w][v] = d;
 38     }
 39 }
 40 
 41 void deleteGraph()
 42 {
 43     for (int i = 0; i < N; i++)
 44         delete G[i];
 45     delete G;
46  }
 ​​47  
48  int findMinDist( int dist[])
 49 { /* Return the vertex with the smallest dist among the vertices not included in MST */ 
50      int minV, v;
 51      int minDist = INT_MAX;
 52      for (v = 0 ; v < N; v++ )
 53      {
 54          if (dist[v] != 0 && dist[v] < minDist)
 55          {
 56              minDist = dist[v];
 57              minV = v;
 58          }
59      }
 60      if (minDist < INT_MAX)
 61          return minV;
 62      return - 1 ;
 63  }
 64  
65  int prim()
 66 { /* return the weight of the minimum spanning tree */ 
67      int v, w, vCount = 0 ;
 68      int totalWeight = 0 ;
 69      int * dist = new  int [N];
 70  
71      /* Initialization, the index of the initial point is 0 */ 
72      for (v =0 ; v < N; v++ )
 73          dist[v] = G[ 0 ][v];
 74  
75      /* Include 0 into the minimum spanning tree MST */ 
76      dist[ 0 ] = 0 ;
 77      vCount++ ;
 78  
79      while ( true )
 80      {
 81          v = findMinDist(dist);
 82          if (v == - 1 )
 83              break ;
 84  
85          totalWeight += dist[v];
 86          dist[v] =0 ; // include v 
87          vCount++ ;
 88  
89          for (w = 0 ; w < N; w++ )
 90          {
 91              /* if w is not included */ 
92              if (dist[w] != 0 && G[v] [w] < dist[w])
 93              {
 94                  dist[w] = G[v][w];
 95              }
 96          }
 97      }
 98  
99      delete dist;
 100  
101      if (vCount < N)
102         return -1;
103     return totalWeight;
104 }