libs/minisat/Heap.h

   1 /******************************************************************************************[Heap.h]
   2 Copyright (c) 2003-2006, Niklas Een, Niklas Sorensson
   3 Copyright (c) 2007-2010, Niklas Sorensson
   4
   5 Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
   6 associated documentation files (the "Software"), to deal in the Software without restriction,
   7 including without limitation the rights to use, copy, modify, merge, publish, distribute,
   8 sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
   9 furnished to do so, subject to the following conditions:
  10
  11 The above copyright notice and this permission notice shall be included in all copies or
  12 substantial portions of the Software.
  13
  14 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT
  15 NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  16 NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
  17 DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT
  18 OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  19 **************************************************************************************************/
  20
  21 #ifndef Minisat_Heap_h
  22 #define Minisat_Heap_h
  23
  24 #include "Vec.h"
  25 #include "IntMap.h"
  26
  27 namespace Minisat {
  28
  29 //=================================================================================================
  30 // A heap implementation with support for decrease/increase key.
  31
  32
  33 template<class K, class Comp, class MkIndex = MkIndexDefault<K> >
  34 class Heap {
  35     vec<K>                heap;     // Heap of Keys
  36     IntMap<K,int,MkIndex> indices;  // Each Key's position (index) in the Heap
  37     Comp                  lt;       // The heap is a minimum-heap with respect to this comparator
  38
  39     // Index "traversal" functions
  40     static inline int left  (int i) { return i*2+1; }
  41     static inline int right (int i) { return (i+1)*2; }
  42     static inline int parent(int i) { return (i-1) >> 1; }
  43
  44
  45     void percolateUp(int i)
  46     {
  47         K   x  = heap[i];
  48         int p  = parent(i);
  49
  50         while (i != 0 && lt(x, heap[p])){
  51             heap[i]          = heap[p];
  52             indices[heap[p]] = i;
  53             i                = p;
  54             p                = parent(p);
  55         }
  56         heap   [i] = x;
  57         indices[x] = i;
  58     }
  59
  60
  61     void percolateDown(int i)
  62     {
  63         K x = heap[i];
  64         while (left(i) < heap.size()){
  65             int child = right(i) < heap.size() && lt(heap[right(i)], heap[left(i)]) ? right(i) : left(i);
  66             if (!lt(heap[child], x)) break;
  67             heap[i]          = heap[child];
  68             indices[heap[i]] = i;
  69             i                = child;
  70         }
  71         heap   [i] = x;
  72         indices[x] = i;
  73     }
  74
  75
  76   public:
  77     Heap(const Comp& c, MkIndex _index = MkIndex()) : indices(_index), lt(c) {}
  78
  79     int  size      ()          const { return heap.size(); }
  80     bool empty     ()          const { return heap.size() == 0; }
  81     bool inHeap    (K k)       const { return indices.has(k) && indices[k] >= 0; }
  82     int  operator[](int index) const { assert(index < heap.size()); return heap[index]; }
  83
  84     void decrease  (K k) { assert(inHeap(k)); percolateUp  (indices[k]); }
  85     void increase  (K k) { assert(inHeap(k)); percolateDown(indices[k]); }
  86
  87
  88     // Safe variant of insert/decrease/increase:
  89     void update(K k)
  90     {
  91         if (!inHeap(k))
  92             insert(k);
  93         else {
  94             percolateUp(indices[k]);
  95             percolateDown(indices[k]); }
  96     }
  97
  98
  99     void insert(K k)
 100     {
 101         indices.reserve(k, -1);
 102         assert(!inHeap(k));
 103
 104         indices[k] = heap.size();
 105         heap.push(k);
 106         percolateUp(indices[k]);
 107     }
 108
 109
 110     void remove(K k)
 111     {
 112         assert(inHeap(k));
 113
 114         int k_pos  = indices[k];
 115         indices[k] = -1;
 116
 117         if (k_pos < heap.size()-1){
 118             heap[k_pos]          = heap.last();
 119             indices[heap[k_pos]] = k_pos;
 120             heap.pop();
 121             percolateDown(k_pos);
 122         }else
 123             heap.pop();
 124     }
 125
 126
 127     K removeMin()
 128     {
 129         K x              = heap[0];
 130         heap[0]          = heap.last();
 131         indices[heap[0]] = 0;
 132         indices[x]       = -1;
 133         heap.pop();
 134         if (heap.size() > 1) percolateDown(0);
 135         return x;
 136     }
 137
 138
 139     // Rebuild the heap from scratch, using the elements in 'ns':
 140     void build(const vec<K>& ns) {
 141         for (int i = 0; i < heap.size(); i++)
 142             indices[heap[i]] = -1;
 143         heap.clear();
 144
 145         for (int i = 0; i < ns.size(); i++){
 146             // TODO: this should probably call reserve instead of relying on it being reserved already.
 147             assert(indices.has(ns[i]));
 148             indices[ns[i]] = i;
 149             heap.push(ns[i]); }
 150
 151         for (int i = heap.size() / 2 - 1; i >= 0; i--)
 152             percolateDown(i);
 153     }
 154
 155     void clear(bool dispose = false)
 156     {
 157         // TODO: shouldn't the 'indices' map also be dispose-cleared?
 158         for (int i = 0; i < heap.size(); i++)
 159             indices[heap[i]] = -1;
 160         heap.clear(dispose);
 161     }
 162 };
 163
 164
 165 //=================================================================================================
 166 }
 167
 168 #endif