COIN-OR::LEMON - Graph Library

source: lemon-0.x/src/work/jacint/fib_heap.h @ 217:fc549fac0dd0

Last change on this file since 217:fc549fac0dd0 was 217:fc549fac0dd0, checked in by Alpar Juttner, 16 years ago

Several bugfixes

File size: 8.7 KB
Line 
1// -*- C++ -*-
2/*
3 *template <typename Item,
4 *          typename Prio,
5 *          typename ItemIntMap,
6 *          typename Compare = std::less<Prio> >
7 *
8 *constructors:
9 *
10 *FibHeap(ItemIntMap),   FibHeap(ItemIntMap, Compare)
11 *
12 *Member functions:
13 *
14 *int size() : returns the number of elements in the heap
15 *
16 *bool empty() : true iff size()=0
17 *
18 *void set(Item, Prio) : calls push(Item, Prio) if Item is not
19 *     in the heap, and calls decrease/increase(Item, Prio) otherwise
20 *
21 *void push(Item, Prio) : pushes Item to the heap with priority Prio. Item
22 *     mustn't be in the heap.
23 *
24 *Item top() : returns the Item with least Prio.
25 *     Must be called only if heap is nonempty.
26 *
27 *Prio prio() : returns the least Prio
28 *     Must be called only if heap is nonempty.
29 *
30 *Prio get(Item) : returns Prio of Item
31 *     Must be called only if Item is in heap.
32 *
33 *void pop() : deletes the Item with least Prio
34 *
35 *void erase(Item) : deletes Item from the heap if it was already there
36 *
37 *void decrease(Item, P) : decreases prio of Item to P.
38 *     Item must be in the heap with prio at least P.
39 *
40 *void increase(Item, P) : sets prio of Item to P.
41 *
42 *state_enum state(Item) : returns PRE_HEAP if Item has not been in the
43 *     heap until now, IN_HEAP if it is in the heap at the moment, and
44 *     POST_HEAP otherwise. In the latter case it is possible that Item
45 *     will get back to the heap again.
46 *
47 *In Fibonacci heaps, increase and erase are not efficient, in case of
48 *many calls to these operations, it is better to use bin_heap.
49 */
50
51#ifndef FIB_HEAP_H
52#define FIB_HEAP_H
53
54#include <vector>
55#include <functional>
56#include <math.h>
57
58namespace hugo {
59 
60  template <typename Item, typename Prio, typename ItemIntMap,
61    typename Compare = std::less<Prio> >
62 
63  class FibHeap {
64 
65    typedef Prio PrioType;
66   
67    class store;
68   
69    std::vector<store> container;
70    int minimum;
71    ItemIntMap &iimap;
72    Compare comp;
73    int num_items;
74
75    enum state_enum {
76      IN_HEAP = 0,
77      PRE_HEAP = -1,
78      POST_HEAP = -2
79    };
80   
81  public :
82   
83    FibHeap(ItemIntMap &_iimap) : minimum(), iimap(_iimap), num_items() {}
84    FibHeap(ItemIntMap &_iimap, const Compare &_comp) : minimum(),
85      iimap(_iimap), comp(_comp), num_items() {}
86   
87   
88    int size() const {
89      return num_items;
90    }
91
92
93    bool empty() const { return num_items==0; }
94
95
96    void set (Item const it, PrioType const value) {
97      int i=iimap[it];
98      if ( i >= 0 && container[i].in ) {
99        if ( comp(value, container[i].prio) ) decrease(it, value);
100        if ( comp(container[i].prio, value) ) increase(it, value);
101      } else push(it, value);
102    }
103   
104
105    void push (Item const it, PrioType const value) {
106      int i=iimap[it];     
107      if ( i < 0 ) {
108        int s=container.size();
109        iimap.set( it, s );     
110        store st;
111        st.name=it;
112        container.push_back(st);
113        i=s;
114      } else {
115        container[i].parent=container[i].child=-1;
116        container[i].degree=0;
117        container[i].in=true;
118        container[i].marked=false;
119      }
120
121      if ( num_items ) {
122        container[container[minimum].right_neighbor].left_neighbor=i;
123        container[i].right_neighbor=container[minimum].right_neighbor;
124        container[minimum].right_neighbor=i;
125        container[i].left_neighbor=minimum;
126        if ( comp( value, container[minimum].prio) ) minimum=i;
127      } else {
128        container[i].right_neighbor=container[i].left_neighbor=i;
129        minimum=i;     
130      }
131      container[i].prio=value;
132      ++num_items;
133    }
134   
135
136    Item top() const {
137      return container[minimum].name;
138    }
139   
140   
141    PrioType prio() const {
142      return container[minimum].prio;
143    }
144   
145
146
147
148    PrioType& operator[](const Item& it) {
149      return container[iimap[it]].prio;
150    }
151   
152    const PrioType& operator[](const Item& it) const {
153      return container[iimap[it]].prio;
154    }
155
156//     const PrioType get(const Item& it) const {
157//       return container[iimap[it]].prio;
158//     }
159
160    void pop() {
161      /*The first case is that there are only one root.*/
162      if ( container[minimum].left_neighbor==minimum ) {
163        container[minimum].in=false;
164        if ( container[minimum].degree!=0 ) {
165          makeroot(container[minimum].child);
166          minimum=container[minimum].child;
167          balance();
168        }
169      } else {
170        int right=container[minimum].right_neighbor;
171        unlace(minimum);
172        container[minimum].in=false;
173        if ( container[minimum].degree > 0 ) {
174          int left=container[minimum].left_neighbor;
175          int child=container[minimum].child;
176          int last_child=container[child].left_neighbor;
177       
178          makeroot(child);
179         
180          container[left].right_neighbor=child;
181          container[child].left_neighbor=left;
182          container[right].left_neighbor=last_child;
183          container[last_child].right_neighbor=right;
184        }
185        minimum=right;
186        balance();
187      } // the case where there are more roots
188      --num_items;   
189    }
190
191   
192    void erase (const Item& it) {
193      int i=iimap[it];
194     
195      if ( i >= 0 && container[i].in ) {       
196        if ( container[i].parent!=-1 ) {
197          int p=container[i].parent;
198          cut(i,p);         
199          cascade(p);
200        }
201        minimum=i;     //As if its prio would be -infinity
202        pop();
203      }
204    }
205   
206
207    void decrease (Item it, PrioType const value) {
208      int i=iimap[it];
209      container[i].prio=value;
210      int p=container[i].parent;
211     
212      if ( p!=-1 && comp(value, container[p].prio) ) {
213        cut(i,p);           
214        cascade(p);
215      }     
216      if ( comp(value, container[minimum].prio) ) minimum=i;
217    }
218   
219
220    void increase (Item it, PrioType const value) {
221      erase(it);
222      push(it, value);
223    }
224
225
226    state_enum state(const Item &it) const {
227      int i=iimap[it];
228      if( i>=0 ) {
229        if ( container[i].in ) i=0;
230        else i=-2;
231      }
232      return state_enum(i);
233    }
234
235
236  private:
237   
238    void balance() {     
239
240    int maxdeg=int( floor( 2.08*log(double(container.size()))))+1;
241 
242    std::vector<int> A(maxdeg,-1);
243   
244    /*
245     *Recall that now minimum does not point to the minimum prio element.
246     *We set minimum to this during balance().
247     */
248    int anchor=container[minimum].left_neighbor;
249    int next=minimum;
250    bool end=false;
251       
252       do {
253        int active=next;
254        if ( anchor==active ) end=true;
255        int d=container[active].degree;
256        next=container[active].right_neighbor;
257
258        while (A[d]!=-1) {       
259          if( comp(container[active].prio, container[A[d]].prio) ) {
260            fuse(active,A[d]);
261          } else {
262            fuse(A[d],active);
263            active=A[d];
264          }
265          A[d]=-1;
266          ++d;
267        }       
268        A[d]=active;
269       } while ( !end );
270
271
272       while ( container[minimum].parent >=0 ) minimum=container[minimum].parent;
273       int s=minimum;
274       int m=minimum;
275       do { 
276         if ( comp(container[s].prio, container[minimum].prio) ) minimum=s;
277         s=container[s].right_neighbor;
278       } while ( s != m );
279    }
280
281
282    void makeroot (int c) {
283      int s=c;
284      do { 
285        container[s].parent=-1;
286        s=container[s].right_neighbor;
287      } while ( s != c );
288    }
289   
290
291    void cut (int a, int b) {   
292      /*
293       *Replacing a from the children of b.
294       */
295      --container[b].degree;
296     
297      if ( container[b].degree !=0 ) {
298        int child=container[b].child;
299        if ( child==a )
300          container[b].child=container[child].right_neighbor;
301        unlace(a);
302      }
303     
304     
305      /*Lacing a to the roots.*/
306      int right=container[minimum].right_neighbor;
307      container[minimum].right_neighbor=a;
308      container[a].left_neighbor=minimum;
309      container[a].right_neighbor=right;
310      container[right].left_neighbor=a;
311
312      container[a].parent=-1;
313      container[a].marked=false;
314    }
315
316
317    void cascade (int a)
318    {
319      if ( container[a].parent!=-1 ) {
320        int p=container[a].parent;
321       
322        if ( container[a].marked==false ) container[a].marked=true;
323        else {
324          cut(a,p);
325          cascade(p);
326        }
327      }
328    }
329
330
331    void fuse (int a, int b) {
332      unlace(b);
333     
334      /*Lacing b under a.*/
335      container[b].parent=a;
336
337      if (container[a].degree==0) {
338        container[b].left_neighbor=b;
339        container[b].right_neighbor=b;
340        container[a].child=b;   
341      } else {
342        int child=container[a].child;
343        int last_child=container[child].left_neighbor;
344        container[child].left_neighbor=b;
345        container[b].right_neighbor=child;
346        container[last_child].right_neighbor=b;
347        container[b].left_neighbor=last_child;
348      }
349
350      ++container[a].degree;
351     
352      container[b].marked=false;
353    }
354
355
356    /*
357     *It is invoked only if a has siblings.
358     */
359    void unlace (int a) {     
360      int leftn=container[a].left_neighbor;
361      int rightn=container[a].right_neighbor;
362      container[leftn].right_neighbor=rightn;
363      container[rightn].left_neighbor=leftn;
364    }
365
366
367    class store {
368      friend class FibHeap;
369     
370      Item name;
371      int parent;
372      int left_neighbor;
373      int right_neighbor;
374      int child;
375      int degree; 
376      bool marked;
377      bool in;
378      PrioType prio;
379
380      store() : parent(-1), child(-1), degree(), marked(false), in(true) {}
381    };
382   
383  };
384 
385} //namespace hugo
386#endif
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