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
|
// CookieJar - A contestant's algorithm toolbox
// Copyright (c) 2013 Peter Szilagyi. All rights reserved.
//
// CookieJar is dual licensed: 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.
//
// The toolbox 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.
//
// Alternatively, the CookieJar toolbox may be used in accordance with the terms
// and conditions contained in a signed written agreement between you and the
// author(s).
package prque
// The size of a block of data
const blockSize = 4096
// A prioritized item in the sorted stack.
type item struct {
value interface{}
priority float32
}
// Internal sortable stack data structure. Implements the Push and Pop ops for
// the stack (heap) functionality and the Len, Less and Swap methods for the
// sortability requirements of the heaps.
type sstack struct {
size int
capacity int
offset int
blocks [][]*item
active []*item
}
// Creates a new, empty stack.
func newSstack() *sstack {
result := new(sstack)
result.active = make([]*item, blockSize)
result.blocks = [][]*item{result.active}
result.capacity = blockSize
return result
}
// Pushes a value onto the stack, expanding it if necessary. Required by
// heap.Interface.
func (s *sstack) Push(data interface{}) {
if s.size == s.capacity {
s.active = make([]*item, blockSize)
s.blocks = append(s.blocks, s.active)
s.capacity += blockSize
s.offset = 0
} else if s.offset == blockSize {
s.active = s.blocks[s.size/blockSize]
s.offset = 0
}
s.active[s.offset] = data.(*item)
s.offset++
s.size++
}
// Pops a value off the stack and returns it. Currently no shrinking is done.
// Required by heap.Interface.
func (s *sstack) Pop() (res interface{}) {
s.size--
s.offset--
if s.offset < 0 {
s.offset = blockSize - 1
s.active = s.blocks[s.size/blockSize]
}
res, s.active[s.offset] = s.active[s.offset], nil
return
}
// Returns the length of the stack. Required by sort.Interface.
func (s *sstack) Len() int {
return s.size
}
// Compares the priority of two elements of the stack (higher is first).
// Required by sort.Interface.
func (s *sstack) Less(i, j int) bool {
return s.blocks[i/blockSize][i%blockSize].priority > s.blocks[j/blockSize][j%blockSize].priority
}
// Swapts two elements in the stack. Required by sort.Interface.
func (s *sstack) Swap(i, j int) {
ib, io, jb, jo := i/blockSize, i%blockSize, j/blockSize, j%blockSize
s.blocks[ib][io], s.blocks[jb][jo] = s.blocks[jb][jo], s.blocks[ib][io]
}
// Resets the stack, effectively clearing its contents.
func (s *sstack) Reset() {
s.size = 0
s.offset = 0
s.active = s.blocks[0]
s.capacity = blockSize
}
|