/usr/include/leptonica/heap.h is in libleptonica-dev 1.74.1-1.
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- Copyright (C) 2001 Leptonica. All rights reserved.
-
- Redistribution and use in source and binary forms, with or without
- modification, are permitted provided that the following conditions
- are met:
- 1. Redistributions of source code must retain the above copyright
- notice, this list of conditions and the following disclaimer.
- 2. Redistributions in binary form must reproduce the above
- copyright notice, this list of conditions and the following
- disclaimer in the documentation and/or other materials
- provided with the distribution.
-
- THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
- A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL ANY
- CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
- EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
- PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
- PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
- OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
- NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
- SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*====================================================================*/
#ifndef LEPTONICA_HEAP_H
#define LEPTONICA_HEAP_H
/*!
* \file heap.h
*
* <pre>
* Expandable priority queue configured as a heap for arbitrary void* data
*
* The L_Heap is used to implement a priority queue. The elements
* in the heap are ordered in either increasing or decreasing key value.
* The key is a float field 'keyval' that is required to be
* contained in the elements of the queue.
*
* The heap is a simple binary tree with the following constraints:
* - the key of each node is >= the keys of the two children
* - the tree is complete, meaning that each level (1, 2, 4, ...)
* is filled and the last level is filled from left to right
*
* The tree structure is implicit in the queue array, with the
* array elements numbered as a breadth-first search of the tree
* from left to right. It is thus guaranteed that the largest
* (or smallest) key belongs to the first element in the array.
*
* Heap sort is used to sort the array. Once an array has been
* sorted as a heap, it is convenient to use it as a priority queue,
* because the min (or max) elements are always at the root of
* the tree (element 0), and once removed, the heap can be
* resorted in not more than log[n] steps, where n is the number
* of elements on the heap. Likewise, if an arbitrary element is
* added to the end of the array A, the sorted heap can be restored
* in not more than log[n] steps.
*
* A L_Heap differs from a L_Queue in that the elements in the former
* are sorted by a key. Internally, the array is maintained
* as a queue, with a pointer to the end of the array. The
* head of the array always remains at array[0]. The array is
* maintained (sorted) as a heap. When an item is removed from
* the head, the last item takes its place (thus reducing the
* array length by 1), and this is followed by array element
* swaps to restore the heap property. When an item is added,
* it goes at the end of the array, and is swapped up to restore
* the heap. If the ptr array is full, adding another item causes
* the ptr array size to double.
*
* For further implementation details, see heap.c.
* </pre>
*/
/*! Heap of arbitrary void* data */
struct L_Heap
{
l_int32 nalloc; /*!< size of allocated ptr array */
l_int32 n; /*!< number of elements stored in the heap */
void **array; /*!< ptr array */
l_int32 direction; /*!< L_SORT_INCREASING or L_SORT_DECREASING */
};
typedef struct L_Heap L_HEAP;
#endif /* LEPTONICA_HEAP_H */
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