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
|
// Copyright ©2012 The bíogo Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package graph
// Visit is a function type that is used by a BreadthFirst or DepthFirst to allow side-effects
// on visiting new nodes in a graph traversal.
type Visit func(u, v Node)
// BreadthFirst is a type that can perform a breadth-first search on a graph.
type BreadthFirst struct {
q *queue
visits []bool
}
// NewBreadthFirst creates a new BreadthFirst searcher.
func NewBreadthFirst() *BreadthFirst {
return &BreadthFirst{q: &queue{}}
}
// Search searches a graph starting from node s until the NodeFilter function nf returns a value of
// true, traversing edges in the graph that allow the Edgefilter function ef to return true. On success
// the terminating node, t is returned. If vo is not nil, it is called with the start and end nodes of an
// edge when the end node has not already been visited.
func (b *BreadthFirst) Search(s Node, ef EdgeFilter, nf NodeFilter, vo Visit) Node {
b.q.Enqueue(s)
b.visits = mark(s, b.visits)
for b.q.Len() > 0 {
t, err := b.q.Dequeue()
if err != nil {
panic(err)
}
if nf != nil && nf(t) {
return t
}
for _, n := range t.Neighbors(ef) {
if !b.Visited(n) {
if vo != nil {
vo(t, n)
}
b.visits = mark(n, b.visits)
b.q.Enqueue(n)
}
}
}
return nil
}
// Visited returns whether the node n has been visited by the searcher.
func (b *BreadthFirst) Visited(n Node) bool {
id := n.ID()
if id < 0 || id >= len(b.visits) {
return false
}
return b.visits[id]
}
// Reset clears the search queue and visited list.
func (b *BreadthFirst) Reset() {
b.q.Clear()
b.visits = b.visits[:0]
}
// DepthFirst is a type that can perform a depth-first search on a graph.
type DepthFirst struct {
s *stack
visits []bool
}
// NewDepthFirst creates a new DepthFirst searcher.
func NewDepthFirst() *DepthFirst {
return &DepthFirst{s: &stack{}}
}
// Search searches a graph starting from node s until the NodeFilter function nf returns a value of
// true, traversing edges in the graph that allow the Edgefilter function ef to return true. On success
// the terminating node, t is returned. If vo is not nil, it is called with the start and end nodes of an
// edge when the end node has not already been visited.
func (d *DepthFirst) Search(s Node, ef EdgeFilter, nf NodeFilter, vo Visit) Node {
d.s.Push(s)
d.visits = mark(s, d.visits)
for d.s.Len() > 0 {
t, err := d.s.Pop()
if err != nil {
panic(err)
}
if nf != nil && nf(t) {
return t
}
for _, n := range t.Neighbors(ef) {
if !d.Visited(n) {
if vo != nil {
vo(t, n)
}
d.visits = mark(n, d.visits)
d.s.Push(n)
}
}
}
return nil
}
// Visited returns whether the node n has been visited by the searcher.
func (d *DepthFirst) Visited(n Node) bool {
id := n.ID()
if id < 0 || id >= len(d.visits) {
return false
}
return d.visits[id]
}
// Reset clears the search stack and visited list.
func (d *DepthFirst) Reset() {
d.s.Clear()
d.visits = d.visits[:0]
}
func mark(n Node, v []bool) []bool {
id := n.ID()
switch {
case id == len(v):
v = append(v, true)
case id > len(v):
t := make([]bool, id+1)
copy(t, v)
v = t
v[id] = true
default:
v[id] = true
}
return v
}
|
