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deque.go
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deque.go
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package utils
import (
"fmt"
"strings"
)
// DNode represents the double linked node
type DNode struct {
Val interface{}
Prev, Next *DNode
}
// Deque is the double ended queue
type Deque struct {
head, tail *DNode
n int
}
func NewDeque() *Deque {
head, tail := &DNode{}, &DNode{}
head.Next = tail
tail.Prev = head
return &Deque{
head: head,
tail: tail,
}
}
func (deq *Deque) String() string {
cur := deq.head.Next
var sb strings.Builder
for cur != deq.tail {
fmt.Fprintf(&sb, "%d=", cur.Val.(int))
cur = cur.Next
}
return sb.String()
}
// IsEmpty check deque is empty or not
func (deq *Deque) IsEmpty() bool {
return deq.n == 0
}
// PushFront push val at front
func (deq *Deque) PushFront(val interface{}) {
node := &DNode{Val: val, Prev: deq.head, Next: deq.head.Next}
deq.head.Next.Prev = node
deq.head.Next = node
deq.n++
}
// PushBack push val at back
func (deq *Deque) PushBack(val interface{}) {
node := &DNode{Val: val, Next: deq.tail, Prev: deq.tail.Prev}
deq.tail.Prev.Next = node
deq.tail.Prev = node
deq.n++
}
func (deq *Deque) PopBack() interface{} {
if deq.n == 0 {
return nil
}
node := deq.tail.Prev
node.Prev.Next = deq.tail
deq.tail.Prev = node.Prev
deq.n--
return node.Val
}
func (deq *Deque) PopFront() interface{} {
if deq.n == 0 {
return nil
}
node := deq.head.Next
node.Next.Prev = deq.head
deq.head.Next = node.Next
deq.n--
return node.Val
}
func (deq *Deque) Back() interface{} {
if deq.n == 0 {
return nil
}
return deq.tail.Prev.Val
}
func (deq *Deque) Front() interface{} {
if deq.n == 0 {
return nil
}
return deq.head.Next.Val
}