sat-solver/BasicHeap.h

/******************************************************************************************[Heap.h]
MiniSat -- Copyright (c) 2003-2006, Niklas Een, Niklas Sorensson

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**************************************************************************************************/

#ifndef BasicHeap_h
#define BasicHeap_h

#include "Vec.h"

//=================================================================================================
// A heap implementation with support for decrease/increase key.


template<class Comp>
class BasicHeap {
    Comp     lt;
    vec<int> heap;     // heap of ints

    // 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; }

    inline void percolateUp(int i)
    {
        int x = heap[i];
        while (i != 0 && lt(x, heap[parent(i)])){
            heap[i]          = heap[parent(i)];
            i                = parent(i);
        }
        heap   [i] = x;
    }


    inline 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];
            i                = child;
        }
        heap[i] = x;
    }


    bool heapProperty(int i) {
        return i >= heap.size()
            || ((i == 0 || !lt(heap[i], heap[parent(i)])) && heapProperty(left(i)) && heapProperty(right(i))); }


  public:
    BasicHeap(const C& c) : comp(c) { }

    int  size      ()                     const { return heap.size(); }
    bool empty     ()                     const { return heap.size() == 0; }
    int  operator[](int index)            const { return heap[index+1]; }
    void clear     (bool dealloc = false)       { heap.clear(dealloc); }
    void insert    (int n)                      { heap.push(n); percolateUp(heap.size()-1); }


    int  removeMin() {
        int r   = heap[0];
        heap[0] = heap.last();
        heap.pop();
        if (heap.size() > 1) percolateDown(0);
        return r; 
    }


    // DEBUG: consistency checking
    bool heapProperty() {
        return heapProperty(1); }


    // COMPAT: should be removed
    int  getmin    ()      { return removeMin(); }
};


//=================================================================================================
#endif