basic

Queue

Nice to solve before

Stack

Instructions

Implement a queue data structure. Adding to the queue should store an element until it is removed. First element added to a queue will be the first that is removed (FIFO). The queue should be a class with methods:

• add method - adds element to a queue (enqueue the element)
• remove method - removes the element from a queue (enqueue the element)
• peek method - returns last element (the one that should be returned) without removing it from the queue
• isEmpty method - return true if queue is empty, otherwise return false

The queue can be implemented in few different ways by using different underlying data structures. Implement each of them:

• List
• Linked list
• Two Stacks

Challenge | Solution

Examples

Example 1

queue = Queue.new
queue.add(1)
queue.remove # 1
queue.remove # null

Example 2

queue = Queue.new
queue.empty? # true
queue.add('A')
queue.empty? # false
queue.add('B')
queue.add('C')
queue.remove # A
queue.peek # A
queue.peek # A
queue.remove # B
queue.remove # C
queue.remove # null