mirror of
https://github.com/tesseract-ocr/tesseract.git
synced 2024-12-21 05:21:35 +08:00
ca083a0897
git-svn-id: https://tesseract-ocr.googlecode.com/svn/trunk@582 d0cd1f9f-072b-0410-8dd7-cf729c803f20
74 lines
3.6 KiB
C
74 lines
3.6 KiB
C
/*====================================================================*
|
|
- Copyright (C) 2001 Leptonica. All rights reserved.
|
|
- This software is distributed in the hope that it will be
|
|
- useful, but with NO WARRANTY OF ANY KIND.
|
|
- No author or distributor accepts responsibility to anyone for the
|
|
- consequences of using this software, or for whether it serves any
|
|
- particular purpose or works at all, unless he or she says so in
|
|
- writing. Everyone is granted permission to copy, modify and
|
|
- redistribute this source code, for commercial or non-commercial
|
|
- purposes, with the following restrictions: (1) the origin of this
|
|
- source code must not be misrepresented; (2) modified versions must
|
|
- be plainly marked as such; and (3) this notice may not be removed
|
|
- or altered from any source or modified source distribution.
|
|
*====================================================================*/
|
|
|
|
#ifndef LEPTONICA_HEAP_H
|
|
#define LEPTONICA_HEAP_H
|
|
|
|
/*
|
|
* heap.h
|
|
*
|
|
* 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.
|
|
*/
|
|
|
|
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 */
|