Golang | Queue

queue.go

package main

type Queue interface {
	Size() int
	IsEmpty() bool
	Enqueue(v interface{})
	Dequeue() interface{}
}

type node struct {
	value interface{}
	next  *node
}

type queue struct {
	head *node
	tail *node
	size int
}

func NewQueue() Queue {
	return &queue{
		head: nil,
		tail: nil,
		size: 0,
	}
}

func (q *queue) Size() int {
	return q.size
}

func (q *queue) IsEmpty() bool {
	return q.size == 0
}

func (q *queue) Enqueue(v interface{}) {
	nn := &node{
		value: v,
		next:  nil,
	}

	if q.head == nil && q.tail == nil {
		q.head = nn
		q.tail = nn
	} else {
		q.tail.next = nn
		q.tail = nn
	}

	q.size++
}

func (q *queue) Dequeue() interface{} {
	if q.size == 0 {
		return nil
	}

	var temp *node
	if q.size == 1 {
		temp = q.head
		q.head = nil
		q.tail = nil
	} else {
		temp = q.head
		q.head = q.head.next
		temp.next = nil
	}
	q.size--
	return temp.value
}

type Queue interface {
	Size() int
	IsEmpty() bool
	Enqueue(v interface{})
	Dequeue() interface{}
        Peek() interface{}
}

type node struct {
	value interface{}
	next  *node
}

type queue struct {
	head *node
	tail *node
	size int
}

func NewQueue() Queue {
	return &queue{
		head: nil,
		tail: nil,
		size: 0,
	}
}

func (q *queue) Size() int {
	return q.size
}

func (q *queue) IsEmpty() bool {
	return q.size == 0
}

func (q *queue) Enqueue(v interface{}) {
	nn := &node{
		value: v,
		next:  nil,
	}

	if q.head == nil && q.tail == nil {
		q.head = nn
		q.tail = nn
	} else {
		q.tail.next = nn
		q.tail = nn
	}

	q.size++
}

func (q *queue) Dequeue() interface{} {
	if q.size == 0 {
		return nil
	}

	var temp *node
	if q.size == 1 {
		temp = q.head
		q.head = nil
		q.tail = nil
	} else {
		temp = q.head
		q.head = q.head.next
		temp.next = nil
	}
	q.size--
	return temp.value
}

func (q *queue) Peek() interface{} {
      if q.size == 0 {
          return nil 
      }
      return q.head.value
}