src/prop/minisat/mtl/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 "base/check.h"
  25 #include "prop/minisat/mtl/Vec.h"
  26
  27 namespace CVC5 {
  28 namespace Minisat {
  29
  30 //=================================================================================================
  31 // A heap implementation with support for decrease/increase key.
  32
  33
  34 template<class Comp>
  35 class Heap {
  36     Comp     lt;       // The heap is a minimum-heap with respect to this comparator
  37     vec<int> heap;     // Heap of integers
  38     vec<int> indices;  // Each integers position (index) in the Heap
  39
  40     // Index "traversal" functions
  41     static inline int left  (int i) { return i*2+1; }
  42     static inline int right (int i) { return (i+1)*2; }
  43     static inline int parent(int i) { return (i-1) >> 1; }
  44
  45
  46     void percolateUp(int i)
  47     {
  48         int x  = heap[i];
  49         int p  = parent(i);
  50
  51         while (i != 0 && lt(x, heap[p])){
  52             heap[i]          = heap[p];
  53             indices[heap[p]] = i;
  54             i                = p;
  55             p                = parent(p);
  56         }
  57         heap   [i] = x;
  58         indices[x] = i;
  59     }
  60
  61
  62     void percolateDown(int i)
  63     {
  64         int x = heap[i];
  65         while (left(i) < heap.size()){
  66             int child = right(i) < heap.size() && lt(heap[right(i)], heap[left(i)]) ? right(i) : left(i);
  67             if (!lt(heap[child], x)) break;
  68             heap[i]          = heap[child];
  69             indices[heap[i]] = i;
  70             i                = child;
  71         }
  72         heap   [i] = x;
  73         indices[x] = i;
  74     }
  75
  76
  77   public:
  78     Heap(const Comp& c) : lt(c) { }
  79
  80     int  size      ()          const { return heap.size(); }
  81     bool empty     ()          const { return heap.size() == 0; }
  82     bool inHeap    (int n)     const { return n < indices.size() && indices[n] >= 0; }
  83     int operator[](int index) const
  84     {
  85       Assert(index < heap.size());
  86       return heap[index];
  87     }
  88
  89     void decrease(int n)
  90     {
  91       Assert(inHeap(n));
  92       percolateUp(indices[n]);
  93     }
  94     void increase(int n)
  95     {
  96       Assert(inHeap(n));
  97       percolateDown(indices[n]);
  98     }
  99
 100     // Safe variant of insert/decrease/increase:
 101     void update(int n)
 102     {
 103         if (!inHeap(n))
 104             insert(n);
 105         else {
 106             percolateUp(indices[n]);
 107             percolateDown(indices[n]); }
 108     }
 109
 110
 111     void insert(int n)
 112     {
 113         indices.growTo(n+1, -1);
 114         Assert(!inHeap(n));
 115
 116         indices[n] = heap.size();
 117         heap.push(n);
 118         percolateUp(indices[n]);
 119     }
 120
 121
 122     int  removeMin()
 123     {
 124         int x            = heap[0];
 125         heap[0]          = heap.last();
 126         indices[heap[0]] = 0;
 127         indices[x]       = -1;
 128         heap.pop();
 129         if (heap.size() > 1) percolateDown(0);
 130         return x;
 131     }
 132
 133
 134     // Rebuild the heap from scratch, using the elements in 'ns':
 135     void build(vec<int>& ns) {
 136         for (int i = 0; i < heap.size(); i++)
 137             indices[heap[i]] = -1;
 138         heap.clear();
 139
 140         for (int i = 0; i < ns.size(); i++){
 141             indices[ns[i]] = i;
 142             heap.push(ns[i]); }
 143
 144         for (int i = heap.size() / 2 - 1; i >= 0; i--)
 145             percolateDown(i);
 146     }
 147
 148     void clear(bool dealloc = false)
 149     {
 150         for (int i = 0; i < heap.size(); i++)
 151             indices[heap[i]] = -1;
 152         heap.clear(dealloc);
 153     }
 154 };
 155
 156
 157 //=================================================================================================
 158 }
 159 }  // namespace CVC5
 160
 161 #endif