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package queue
type (
Queue struct {
start, end *node
length int
}
node struct {
value interface{}
next *node
}
)
// Create a new queue
func New() *Queue {
return &Queue{nil,nil,0}
}
// Take the next item off the front of the queue
func (this *Queue) Dequeue() interface{} {
if this.length == 0 {
return nil
}
n := this.start
if this.length == 1 {
this.start = nil
this.end = nil
} else {
this.start = this.start.next
}
this.length--
return n.value
}
// Put an item on the end of a queue
func (this *Queue) Enqueue(value interface{}) {
n := &node{value,nil}
if this.length == 0 {
this.start = n
this.end = n
} else {
this.end.next = n
this.end = n
}
this.length++
}
// Return the number of items in the queue
func (this *Queue) Len() int {
return this.length
}
// Return the first item in the queue without removing it
func (this *Queue) Peek() interface{} {
if this.length == 0 {
return nil
}
return this.start.value
}
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