Go Queue

queue.go

package main

import "log"

type Node struct {
	val  int
	next *Node
}

type Queue struct {
	first *Node
	last  *Node
}

func (q Queue) Peek() *Node {
	return q.first
}

func (q *Queue) Remove() *Node {
	if q.IsEmpty() {
		return nil
	}

	val := q.first
	q.first = q.first.next
	if q.first == nil {
		q.last = nil
	}

	return val
}

func (q *Queue) Add(node *Node) {
	if q.last != nil {
		q.last.next = node
	}
	q.last = node

	if q.first == nil {
		q.first = node
	}
}

func (q Queue) IsEmpty() bool {
	return q.first == nil
}

func main() {
	queue := &Queue{}

	assert(true, queue.IsEmpty())
	assert((*Node)(nil), queue.Peek())
	assert((*Node)(nil), queue.Remove())

	queue.Add(&Node{val: 1})
	queue.Add(&Node{val: 2})
	queue.Add(&Node{val: 3})

	assert(false, queue.IsEmpty())
	assert(1, queue.Peek().val)
	assert(1, queue.Remove().val)
	assert(2, queue.Remove().val)
	assert(3, queue.Remove().val)
	assert(true, queue.IsEmpty())
	assert((*Node)(nil), queue.Remove())
}

func assert(expected, actual interface{}) {
	if expected != actual {
		log.Panicf("%s != %s", expected, actual)
	}
}