Challenge Summary

stacks and queues

Author : Rami Zaitoun

Challenge Description

• Create a Node class that has properties for the value stored in the Node, and a pointer to the next node.
• Create a Stack class that has a top property. It creates an empty Stack when instantiated.
• This object should be aware of a default empty value assigned to top when the stack is created.
• Define a method called push which takes any value as an argument and adds a new node with that value to the top of the stack with an O(1) Time performance.
• Define a method called pop that does not take any argument, removes the node from the top of the stack, and returns the node’s value.
• Should raise exception when called on empty stack
• Define a method called peek that does not take an argument and returns the value of the node located on top of the stack, without removing it from the stack.
• Should raise exception when called on empty stack
• Define a method called isEmpty that takes no argument, and returns a boolean indicating whether or not the stack is empty.
• Create a Queue class that has a front property. It creates an empty Queue when instantiated.
• This object should be aware of a default empty value assigned to front when the queue is created.
• Define a method called enqueue which takes any value as an argument and adds a new node with that value to the back of the queue with an O(1) Time performance.
• Define a method called dequeue that does not take any argument, removes the node from the front of the queue, and returns the node’s value.
• Should raise exception when called on empty queue
• Define a method called peek that does not take an argument and returns the value of the node located in the front of the queue, without removing it from the queue.
• Should raise exception when called on empty queue
• Define a method called isEmpty that takes no argument, and returns a boolean indicating whether or not the queue is empty.

Approach & Efficiency

Stack method	Big O	Queue method	Big O
push(value)	O(1)	enqueue(value)	O(1)
pop()	O(1)	dequeue()	O(1)
peek()	O(1)	peek()	O(1)
isEmpty()	O(1)	isEmpty()	O(1)

Solution

Structure and Testing

Utilize the Single-responsibility principle: any methods you write should be clean, reusable, abstract component parts to the whole challenge. You will be given feedback and marked down if you attempt to define a large, complex algorithm in one function definition.

Write tests to prove the following functionality:

• Can successfully push onto a stack
• Can successfully push multiple values onto a stack
• Can successfully pop off the stack
• Can successfully empty a stack after multiple pops
• Can successfully peek the next item on the stack
• Can successfully instantiate an empty stack
• Calling pop or peek on empty stack raises exception
• Can successfully enqueue into a queue
• Can successfully enqueue multiple values into a queue
• Can successfully dequeue out of a queue the expected value
• Can successfully peek into a queue, seeing the expected value
• Can successfully empty a queue after multiple dequeues
• Can successfully instantiate an empty queue
• Calling dequeue or peek on empty queue raises exception