heap.h

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 * Copyright 2008-2009  Marius Muja (mariusm@cs.ubc.ca). All rights reserved.
 * Copyright 2008-2009  David G. Lowe (lowe@cs.ubc.ca). All rights reserved.
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#ifndef RTABMAP_FLANN_HEAP_H_
#define RTABMAP_FLANN_HEAP_H_

#include <algorithm>
#include <vector>

namespace rtflann
{

template <typename T>
class Heap
{

    std::vector<T> heap;
    int length;

    int count;



public:
    Heap(int size)
    {
        length = size;
        heap.reserve(length);
        count = 0;
    }

    int size()
    {
        return count;
    }

    bool empty()
    {
        return size()==0;
    }

    void clear()
    {
        heap.clear();
        count = 0;
    }

    struct CompareT : public std::binary_function<T,T,bool>
    {
        bool operator()(const T& t_1, const T& t_2) const
        {
            return t_2 < t_1;
        }
    };

    void insert(const T& value)
    {
        /* If heap is full, then return without adding this element. */
        if (count == length) {
            return;
        }

        heap.push_back(value);
        static CompareT compareT;
        std::push_heap(heap.begin(), heap.end(), compareT);
        ++count;
    }



    bool popMin(T& value)
    {
        if (count == 0) {
            return false;
        }

        value = heap[0];
        static CompareT compareT;
        std::pop_heap(heap.begin(), heap.end(), compareT);
        heap.pop_back();
        --count;

        return true;  /* Return old last node. */
    }
};


template <typename T>
class IntervalHeap
{
        struct Interval
        {
                T left;
                T right;
        };

    std::vector<Interval> heap;
    size_t capacity_;
    size_t size_;

public:
    IntervalHeap(int capacity) : capacity_(capacity), size_(0)
    {
        heap.resize(capacity/2 + capacity%2 + 1); // 1-based indexing
    }

    size_t size()
    {
        return size_;
    }

    bool empty()
    {
        return size_==0;
    }

    void clear()
    {
        size_ = 0;
    }

    void insert(const T& value)
    {
        /* If heap is full, then return without adding this element. */
        if (size_ == capacity_) {
            return;
        }

        // insert into the root
        if (size_<2) {
                if (size_==0) {
                        heap[1].left = value;
                        heap[1].right = value;
                }
                else {
                        if (value<heap[1].left) {
                                heap[1].left = value;
                        }
                        else {
                                heap[1].right = value;
                        }
                }
                ++size_;
                return;
        }

        size_t last_pos = size_/2 + size_%2;
        bool min_heap;

        if (size_%2) { // odd number of elements
                min_heap = (value<heap[last_pos].left)? true : false;
        }
        else {
                ++last_pos;
                min_heap = (value<heap[last_pos/2].left)? true : false;
        }

        if (min_heap) {
                size_t pos = last_pos;
                size_t par = pos/2;
                while (pos>1 && value < heap[par].left) {
                        heap[pos].left = heap[par].left;
                        pos = par;
                        par = pos/2;
                }
                heap[pos].left = value;
                ++size_;

                if (size_%2) { // duplicate element in last position if size is odd
                        heap[last_pos].right = heap[last_pos].left;
                }
        }
        else {
                size_t pos = last_pos;
                size_t par = pos/2;
                while (pos>1 && heap[par].right < value) {
                        heap[pos].right = heap[par].right;
                        pos = par;
                        par = pos/2;
                }
                heap[pos].right = value;
                ++size_;

                if (size_%2) { // duplicate element in last position if size is odd
                        heap[last_pos].left = heap[last_pos].right;
                }
        }
    }


    bool popMin(T& value)
    {
        if (size_ == 0) {
            return false;
        }

        value = heap[1].left;
        size_t last_pos = size_/2 + size_%2;
        T elem = heap[last_pos].left;

        if (size_ % 2) { // odd number of elements
                --last_pos;
        }
        else {
                heap[last_pos].left = heap[last_pos].right;
        }
        --size_;
        if (size_<2) return true;

        size_t crt=1; // root node
        size_t child = crt*2;

        while (child <= last_pos) {
                if (child < last_pos && heap[child+1].left < heap[child].left) ++child; // pick the child with min

                if (!(heap[child].left<elem)) break;

                heap[crt].left = heap[child].left;
                if (heap[child].right<elem) {
                        std::swap(elem, heap[child].right);
                }

                crt = child;
                child *= 2;
        }
        heap[crt].left = elem;
        return true;
    }


    bool popMax(T& value)
    {
        if (size_ == 0) {
            return false;
        }

        value = heap[1].right;
        size_t last_pos = size_/2 + size_%2;
        T elem = heap[last_pos].right;

        if (size_%2) { // odd number of elements
                --last_pos;
        }
        else {
                heap[last_pos].right = heap[last_pos].left;
        }
        --size_;
        if (size_<2) return true;

        size_t crt=1; // root node
        size_t child = crt*2;

        while (child <= last_pos) {
                if (child < last_pos && heap[child].right < heap[child+1].right) ++child; // pick the child with max

                if (!(elem < heap[child].right)) break;

                heap[crt].right = heap[child].right;
                if (elem<heap[child].left) {
                        std::swap(elem, heap[child].left);
                }

                crt = child;
                child *= 2;
        }
        heap[crt].right = elem;
        return true;
    }


    bool getMin(T& value)
    {
        if (size_==0) {
                return false;
        }
        value = heap[1].left;
        return true;
    }


    bool getMax(T& value)
    {
        if (size_==0) {
                return false;
        }
        value = heap[1].right;
        return true;
    }
};


template <typename T>
class BoundedHeap
{
        IntervalHeap<T> interval_heap_;
        size_t capacity_;
public:
        BoundedHeap(size_t capacity) : interval_heap_(capacity), capacity_(capacity)
        {

        }

    int size()
    {
        return interval_heap_.size();
    }

    bool empty()
    {
        return interval_heap_.empty();
    }

    void clear()
    {
        interval_heap_.clear();
    }

    void insert(const T& value)
    {
        if (interval_heap_.size()==capacity_) {
                T max;
                interval_heap_.getMax(max);
                if (max<value) return;
                        interval_heap_.popMax(max);
        }
        interval_heap_.insert(value);
    }

    bool popMin(T& value)
    {
        return interval_heap_.popMin(value);
    }
};



}

#endif //FLANN_HEAP_H_