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* Software License Agreement (BSD License)
*
* 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.
*
* THE BSD LICENSE
*
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*
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*************************************************************************/
#ifndef OPENCV_FLANN_HEAP_H_
#define OPENCV_FLANN_HEAP_H_
#include <algorithm>
#include <vector>
namespace cvflann
{
/**
* Priority Queue Implementation
*
* The priority queue is implemented with a heap. A heap is a complete
* (full) binary tree in which each parent is less than both of its
* children, but the order of the children is unspecified.
*/
template <typename T>
class Heap
{
/**
* Storage array for the heap.
* Type T must be comparable.
*/
std::vector<T> heap;
int length;
/**
* Number of element in the heap
*/
int count;
public:
/**
* Constructor.
*
* Params:
* sz = heap size
*/
Heap(int sz)
{
length = sz;
heap.reserve(length);
count = 0;
}
/**
*
* Returns: heap size
*/
int size()
{
return count;
}
/**
* Tests if the heap is empty
*
* Returns: true is heap empty, false otherwise
*/
bool empty()
{
return size()==0;
}
/**
* Clears the heap.
*/
void clear()
{
heap.clear();
count = 0;
}
struct CompareT
{
bool operator()(const T& t_1, const T& t_2) const
{
return t_2 < t_1;
}
};
/**
* Insert a new element in the heap.
*
* We select the next empty leaf node, and then keep moving any larger
* parents down until the right location is found to store this element.
*
* Params:
* value = the new element to be inserted in the heap
*/
void insert(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;
}
/**
* Returns the node of minimum value from the heap (top of the heap).
*
* Params:
* value = out parameter used to return the min element
* Returns: false if heap empty
*/
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. */
}
};
}
#endif //OPENCV_FLANN_HEAP_H_