1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
|
/* Barebones heap implementation supporting only insert and pop.
Copyright (C) 2010-2013 Free Software Foundation, Inc.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
/* Full implementation: GDSL (http://gna.org/projects/gdsl/) by Nicolas
Darnis <ndarnis@free.fr>. */
#include <config.h>
#include "heap.h"
#include "stdlib--.h"
#include "xalloc.h"
static int heap_default_compare (void const *, void const *);
static size_t heapify_down (void **, size_t, size_t,
int (*) (void const *, void const *));
static void heapify_up (void **, size_t,
int (*) (void const *, void const *));
struct heap
{
void **array; /* array[0] is not used */
size_t capacity; /* Array size */
size_t count; /* Used as index to last element. Also is num of items. */
int (*compare) (void const *, void const *);
};
/* Allocate memory for the heap. */
struct heap *
heap_alloc (int (*compare) (void const *, void const *), size_t n_reserve)
{
struct heap *heap = xmalloc (sizeof *heap);
if (n_reserve == 0)
n_reserve = 1;
heap->array = xnmalloc (n_reserve, sizeof *(heap->array));
heap->array[0] = NULL;
heap->capacity = n_reserve;
heap->count = 0;
heap->compare = compare ? compare : heap_default_compare;
return heap;
}
static int
heap_default_compare (void const *a, void const *b)
{
return 0;
}
void
heap_free (struct heap *heap)
{
free (heap->array);
free (heap);
}
/* Insert element into heap. */
int
heap_insert (struct heap *heap, void *item)
{
if (heap->capacity - 1 <= heap->count)
heap->array = x2nrealloc (heap->array, &heap->capacity,
sizeof *(heap->array));
heap->array[++heap->count] = item;
heapify_up (heap->array, heap->count, heap->compare);
return 0;
}
/* Pop top element off heap. */
void *
heap_remove_top (struct heap *heap)
{
void *top;
if (heap->count == 0)
return NULL;
top = heap->array[1];
heap->array[1] = heap->array[heap->count--];
heapify_down (heap->array, heap->count, 1, heap->compare);
return top;
}
/* Move element down into appropriate position in heap. */
static size_t
heapify_down (void **array, size_t count, size_t initial,
int (*compare) (void const *, void const *))
{
void *element = array[initial];
size_t parent = initial;
while (parent <= count / 2)
{
size_t child = 2 * parent;
if (child < count && compare (array[child], array[child+1]) < 0)
child++;
if (compare (array[child], element) <= 0)
break;
array[parent] = array[child];
parent = child;
}
array[parent] = element;
return parent;
}
/* Move element up into appropriate position in heap. */
static void
heapify_up (void **array, size_t count,
int (*compare) (void const *, void const *))
{
size_t k = count;
void *new_element = array[k];
while (k != 1 && compare (array[k/2], new_element) <= 0)
{
array[k] = array[k/2];
k /= 2;
}
array[k] = new_element;
}
|
