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
152
153
|
/*
* Copyright © 2020 Google, Inc.
*
* This is part of HarfBuzz, a text shaping library.
*
* Permission is hereby granted, without written agreement and without
* license or royalty fees, to use, copy, modify, and distribute this
* software and its documentation for any purpose, provided that the
* above copyright notice and the following two paragraphs appear in
* all copies of this software.
*
* IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
* DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
* ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
* IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
* DAMAGE.
*
* THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
* BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
* FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS
* ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
* PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
*
* Google Author(s): Garret Rieger
*/
#ifndef HB_PRIORITY_QUEUE_HH
#define HB_PRIORITY_QUEUE_HH
#include "hb.hh"
#include "hb-vector.hh"
/*
* hb_priority_queue_t
*
* Priority queue implemented as a binary heap. Supports extract minimum
* and insert operations.
*/
struct hb_priority_queue_t
{
private:
typedef hb_pair_t<int64_t, unsigned> item_t;
hb_vector_t<item_t> heap;
public:
void reset () { heap.resize (0); }
bool in_error () const { return heap.in_error (); }
void insert (int64_t priority, unsigned value)
{
heap.push (item_t (priority, value));
if (unlikely (heap.in_error ())) return;
bubble_up (heap.length - 1);
}
item_t pop_minimum ()
{
assert (!is_empty ());
item_t result = heap.arrayZ[0];
heap.arrayZ[0] = heap.arrayZ[heap.length - 1];
heap.shrink (heap.length - 1);
if (!is_empty ())
bubble_down (0);
return result;
}
const item_t& minimum ()
{
return heap[0];
}
bool is_empty () const { return heap.length == 0; }
explicit operator bool () const { return !is_empty (); }
unsigned int get_population () const { return heap.length; }
/* Sink interface. */
hb_priority_queue_t& operator << (item_t item)
{ insert (item.first, item.second); return *this; }
private:
static constexpr unsigned parent (unsigned index)
{
return (index - 1) / 2;
}
static constexpr unsigned left_child (unsigned index)
{
return 2 * index + 1;
}
static constexpr unsigned right_child (unsigned index)
{
return 2 * index + 2;
}
void bubble_down (unsigned index)
{
assert (index < heap.length);
unsigned left = left_child (index);
unsigned right = right_child (index);
bool has_left = left < heap.length;
if (!has_left)
// If there's no left, then there's also no right.
return;
bool has_right = right < heap.length;
if (heap.arrayZ[index].first <= heap.arrayZ[left].first
&& (!has_right || heap.arrayZ[index].first <= heap.arrayZ[right].first))
return;
if (!has_right || heap.arrayZ[left].first < heap.arrayZ[right].first)
{
swap (index, left);
bubble_down (left);
return;
}
swap (index, right);
bubble_down (right);
}
void bubble_up (unsigned index)
{
assert (index < heap.length);
if (index == 0) return;
unsigned parent_index = parent (index);
if (heap.arrayZ[parent_index].first <= heap.arrayZ[index].first)
return;
swap (index, parent_index);
bubble_up (parent_index);
}
void swap (unsigned a, unsigned b)
{
assert (a < heap.length);
assert (b < heap.length);
hb_swap (heap.arrayZ[a], heap.arrayZ[b]);
}
};
#endif /* HB_PRIORITY_QUEUE_HH */
|
