Heap.h

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/******************************************************************************************[Heap.h]
Copyright (c) 2003-2006, Niklas Een, Niklas Sorensson
Copyright (c) 2007-2010, Niklas Sorensson
 
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
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The above copyright notice and this permission notice shall be included in all copies or
substantial portions of the Software.
 
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT
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#ifndef Minisat_Heap_h
#define Minisat_Heap_h
 
#include "sat/bsat2/Vec.h"
 
ABC_NAMESPACE_CXX_HEADER_START
 
namespace Minisat {
 
//=================================================================================================
// A heap implementation with support for decrease/increase key.
 
 
template<class Comp>
class Heap {
    Comp     lt;       // The heap is a minimum-heap with respect to this comparator
    vec<int> heap;     // Heap of integers
    vec<int> indices;  // Each integers position (index) in the Heap
 
    // Index "traversal" functions
    static inline int left  (int i) { return i*2+1; }
    static inline int right (int i) { return (i+1)*2; }
    static inline int parent(int i) { return (i-1) >> 1; }
 
 
    void percolateUp(int i)
    {
        int x  = heap[i];
        int p  = parent(i);
        
        while (i != 0 && lt(x, heap[p])){
            heap[i]          = heap[p];
            indices[heap[p]] = i;
            i                = p;
            p                = parent(p);
        }
        heap   [i] = x;
        indices[x] = i;
    }
 
 
    void percolateDown(int i)
    {
        int x = heap[i];
        while (left(i) < heap.size()){
            int child = right(i) < heap.size() && lt(heap[right(i)], heap[left(i)]) ? right(i) : left(i);
            if (!lt(heap[child], x)) break;
            heap[i]          = heap[child];
            indices[heap[i]] = i;
            i                = child;
        }
        heap   [i] = x;
        indices[x] = i;
    }
 
 
  public:
    Heap(const Comp& c) : lt(c) { }
 
    int  size      ()          const { return heap.size(); }
    bool empty     ()          const { return heap.size() == 0; }
    bool inHeap    (int n)     const { return n < indices.size() && indices[n] >= 0; }
    int  operator[](int index) const { assert(index < heap.size()); return heap[index]; }
 
 
    void decrease  (int n) { assert(inHeap(n)); percolateUp  (indices[n]); }
    void increase  (int n) { assert(inHeap(n)); percolateDown(indices[n]); }
 
 
    // Safe variant of insert/decrease/increase:
    void update(int n)
    {
        if (!inHeap(n))
            insert(n);
        else {
            percolateUp(indices[n]);
            percolateDown(indices[n]); }
    }
 
 
    void insert(int n)
    {
        indices.growTo(n+1, -1);
        assert(!inHeap(n));
 
        indices[n] = heap.size();
        heap.push(n);
        percolateUp(indices[n]); 
    }
 
 
    int  removeMin()
    {
        int x            = heap[0];
        heap[0]          = heap.last();
        indices[heap[0]] = 0;
        indices[x]       = -1;
        heap.pop();
        if (heap.size() > 1) percolateDown(0);
        return x; 
    }
 
 
    // Rebuild the heap from scratch, using the elements in 'ns':
    void build(vec<int>& ns) {
        int i;
        for (i = 0; i < heap.size(); i++)
            indices[heap[i]] = -1;
        heap.clear();
 
        for (i = 0; i < ns.size(); i++){
            indices[ns[i]] = i;
            heap.push(ns[i]); }
 
        for (i = heap.size() / 2 - 1; i >= 0; i--)
            percolateDown(i);
    }
 
    void clear(bool dealloc = false) 
    { 
        for (int i = 0; i < heap.size(); i++)
            indices[heap[i]] = -1;
        heap.clear(dealloc); 
    }
};
 
 
//=================================================================================================
}
 
ABC_NAMESPACE_CXX_HEADER_END
 
#endif