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// 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
import (
"errors"
)
var (
queueIndexOutOfRange = errors.New("graph: queue index out of range")
emptyQueue = errors.New("graph: queue empty")
stackIndexOutOfRange = errors.New("graph: stack index out of range")
emptyStack = errors.New("graph: stack empty")
)
type queue struct {
head int
data []Node
}
func (q *queue) Enqueue(n Node) {
if len(q.data) == cap(q.data) && q.head > 0 {
l := q.Len()
copy(q.data, q.data[q.head:])
q.head = 0
q.data = append(q.data[:l], n)
} else {
q.data = append(q.data, n)
}
}
func (q *queue) Dequeue() (Node, error) {
if q.Len() == 0 {
return nil, emptyQueue
}
var n Node
n, q.data[q.head] = q.data[q.head], nil
q.head++
if q.Len() == 0 {
q.head = 0
q.data = q.data[:0]
}
return n, nil
}
func (q *queue) Peek(i int) (Node, error) {
if i < q.head || i >= len(q.data) {
return nil, queueIndexOutOfRange
}
return q.data[i+q.head], nil
}
func (q *queue) Clear() {
q.head = 0
q.data = q.data[:0]
}
func (q *queue) Len() int { return len(q.data) - q.head }
type stack struct {
data []Node
}
func (s *stack) Push(n Node) { s.data = append(s.data, n) }
func (s *stack) Pop() (Node, error) {
if len(s.data) == 0 {
return nil, emptyStack
}
var n Node
n, s.data, s.data[len(s.data)-1] = s.data[len(s.data)-1], s.data[:len(s.data)-1], nil
return n, nil
}
func (s *stack) Peek(i int) (Node, error) {
if i < 0 || i >= len(s.data) {
return nil, stackIndexOutOfRange
}
return s.data[i], nil
}
func (s *stack) Clear() {
s.data = s.data[:0]
}
func (s *stack) Len() int { return len(s.data) }
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