grdijkm2.cpp

数据结构与算法分析（C++）（版第二版）源码

#include <iostream.h>
#include <stdlib.h>

#include "book.h"

#define INFINITY 65535  // Big enough for simple tests

#include "grmat.h"
#include "minheap.h"

int minVertex(Graph*, int*);

class DijkElem {
public:
  int vertex, distance;
  DijkElem() { vertex = -1; distance = -1; }
  DijkElem(int v, int d) { vertex = v; distance = d; }
};

class DDComp {
public:
  static bool lt(DijkElem x, DijkElem y)
    { return x.distance < y.distance; }
  static bool eq(DijkElem x, DijkElem y)
    { return x.distance == y.distance; }
  static bool gt(DijkElem x, DijkElem y)
    { return x.distance > y.distance; }
};

// Dijkstra's shortest paths algorithm w/ priority queue
void Dijkstra(Graph* G, int* D, int s) {
  int i, v, w;            // v is current vertex
  DijkElem temp;
  DijkElem E[G->e()];     // Heap array with lots of space
  temp.distance = 0; temp.vertex = s;
  E[0] = temp;            // Initialize heap array
  minheap<DijkElem, DDComp> H(E, 1, G->e()); // Create heap
  for (i=0; i<G->n(); i++) {       // Now, get distances
    do {
      if(!H.removemin(temp)) return; // Nothing to remove
      v = temp.vertex;
    } while (G->getMark(v) == VISITED);
    G->setMark(v, VISITED);
    if (D[v] == INFINITY) return;  // Unreachable vertices
    for (w=G->first(v); w<G->n(); w = G->next(v,w))
      if (D[w] > (D[v] + G->weight(v, w))) { // Update D
        D[w] = D[v] + G->weight(v, w);
        temp.distance = D[w]; temp.vertex = w;
        H.insert(temp);    // Insert new distance in heap
      }
  }
}


// Test Depth First Search:
// Version for Adjancency Matrix representation
main(int argc, char** argv) {
  Graph* G;
  FILE *fid;

  if (argc != 2) {
    cout << "Usage: grdijk1m <file>\n";
    exit(-1);
  }

  if ((fid = fopen(argv[1], "rt")) == NULL) {
    cout << "Unable to open file |" << argv[1] << "|\n";
    exit(-1);
  }

  G = createGraph<Graphm>(fid);
  if (G == NULL) {
    cout << "Unable to create graph\n";
    exit(-1);
  }

  int D[G->n()];
  for (int i=0; i<G->n(); i++)     // Initialize
    D[i] = INFINITY;
  D[0] = 0;

  Dijkstra(G, D, 0);
  for(int k=0; k<G->n(); k++)
    cout << D[k] << " ";
  cout << endl;
  return 0;
}