COIN-OR::LEMON - Graph Library

source: lemon-0.x/src/work/jacint/fib_heap.h @ 211:9222a9b8b323

Last change on this file since 211:9222a9b8b323 was 211:9222a9b8b323, checked in by jacint, 16 years ago

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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.get(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.get(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) const {
149      return container[iimap.get(it)].prio;
150    }
151   
152    const PrioType& operator[](const Item& it) const {
153      return container[iimap.get(it)].prio;
154    }
155
156    const PrioType get(const Item& it) const {
157      return container[iimap.get(it)].prio;
158    }
159
160
161
162    void pop() {
163      /*The first case is that there are only one root.*/
164      if ( container[minimum].left_neighbor==minimum ) {
165        container[minimum].in=false;
166        if ( container[minimum].degree!=0 ) {
167          makeroot(container[minimum].child);
168          minimum=container[minimum].child;
169          balance();
170        }
171      } else {
172        int right=container[minimum].right_neighbor;
173        unlace(minimum);
174        container[minimum].in=false;
175        if ( container[minimum].degree > 0 ) {
176          int left=container[minimum].left_neighbor;
177          int child=container[minimum].child;
178          int last_child=container[child].left_neighbor;
179       
180          makeroot(child);
181         
182          container[left].right_neighbor=child;
183          container[child].left_neighbor=left;
184          container[right].left_neighbor=last_child;
185          container[last_child].right_neighbor=right;
186        }
187        minimum=right;
188        balance();
189      } // the case where there are more roots
190      --num_items;   
191    }
192
193   
194    void erase (const Item& it) {
195      int i=iimap.get(it);
196     
197      if ( i >= 0 && container[i].in ) {       
198        if ( container[i].parent!=-1 ) {
199          int p=container[i].parent;
200          cut(i,p);         
201          cascade(p);
202        }
203        minimum=i;     //As if its prio would be -infinity
204        pop();
205      }
206    }
207   
208
209    void decrease (Item it, PrioType const value) {
210      int i=iimap.get(it);
211      container[i].prio=value;
212      int p=container[i].parent;
213     
214      if ( p!=-1 && comp(value, container[p].prio) ) {
215        cut(i,p);           
216        cascade(p);
217      }     
218      if ( comp(value, container[minimum].prio) ) minimum=i;
219    }
220   
221
222    void increase (Item it, PrioType const value) {
223      erase(it);
224      push(it, value);
225    }
226
227
228    state_enum state(const Item &it) const {
229      int i=iimap.get(it);
230      if( i>=0 ) {
231        if ( container[i].in ) i=0;
232        else i=-2;
233      }
234      return state_enum(i);
235    }
236
237
238  private:
239   
240    void balance() {     
241
242    int maxdeg=int( floor( 2.08*log(double(container.size()))))+1;
243 
244    std::vector<int> A(maxdeg,-1);
245   
246    /*
247     *Recall that now minimum does not point to the minimum prio element.
248     *We set minimum to this during balance().
249     */
250    int anchor=container[minimum].left_neighbor;
251    int next=minimum;
252    bool end=false;
253       
254       do {
255        int active=next;
256        if ( anchor==active ) end=true;
257        int d=container[active].degree;
258        next=container[active].right_neighbor;
259
260        while (A[d]!=-1) {       
261          if( comp(container[active].prio, container[A[d]].prio) ) {
262            fuse(active,A[d]);
263          } else {
264            fuse(A[d],active);
265            active=A[d];
266          }
267          A[d]=-1;
268          ++d;
269        }       
270        A[d]=active;
271       } while ( !end );
272
273
274       while ( container[minimum].parent >=0 ) minimum=container[minimum].parent;
275       int s=minimum;
276       int m=minimum;
277       do { 
278         if ( comp(container[s].prio, container[minimum].prio) ) minimum=s;
279         s=container[s].right_neighbor;
280       } while ( s != m );
281    }
282
283
284    void makeroot (int c) {
285      int s=c;
286      do { 
287        container[s].parent=-1;
288        s=container[s].right_neighbor;
289      } while ( s != c );
290    }
291   
292
293    void cut (int a, int b) {   
294      /*
295       *Replacing a from the children of b.
296       */
297      --container[b].degree;
298     
299      if ( container[b].degree !=0 ) {
300        int child=container[b].child;
301        if ( child==a )
302          container[b].child=container[child].right_neighbor;
303        unlace(a);
304      }
305     
306     
307      /*Lacing a to the roots.*/
308      int right=container[minimum].right_neighbor;
309      container[minimum].right_neighbor=a;
310      container[a].left_neighbor=minimum;
311      container[a].right_neighbor=right;
312      container[right].left_neighbor=a;
313
314      container[a].parent=-1;
315      container[a].marked=false;
316    }
317
318
319    void cascade (int a)
320    {
321      if ( container[a].parent!=-1 ) {
322        int p=container[a].parent;
323       
324        if ( container[a].marked==false ) container[a].marked=true;
325        else {
326          cut(a,p);
327          cascade(p);
328        }
329      }
330    }
331
332
333    void fuse (int a, int b) {
334      unlace(b);
335     
336      /*Lacing b under a.*/
337      container[b].parent=a;
338
339      if (container[a].degree==0) {
340        container[b].left_neighbor=b;
341        container[b].right_neighbor=b;
342        container[a].child=b;   
343      } else {
344        int child=container[a].child;
345        int last_child=container[child].left_neighbor;
346        container[child].left_neighbor=b;
347        container[b].right_neighbor=child;
348        container[last_child].right_neighbor=b;
349        container[b].left_neighbor=last_child;
350      }
351
352      ++container[a].degree;
353     
354      container[b].marked=false;
355    }
356
357
358    /*
359     *It is invoked only if a has siblings.
360     */
361    void unlace (int a) {     
362      int leftn=container[a].left_neighbor;
363      int rightn=container[a].right_neighbor;
364      container[leftn].right_neighbor=rightn;
365      container[rightn].left_neighbor=leftn;
366    }
367
368
369    class store {
370      friend class FibHeap;
371     
372      Item name;
373      int parent;
374      int left_neighbor;
375      int right_neighbor;
376      int child;
377      int degree; 
378      bool marked;
379      bool in;
380      PrioType prio;
381
382      store() : parent(-1), child(-1), degree(), marked(false), in(true) {}
383    };
384   
385  };
386 
387} //namespace hugo
388#endif
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