stacks_and_queues

• A queue is a First-In, First-Out (FIFO) abstract data type. The first value added to the queue will be the first value removed from the queue. My queue is implemented by a Queue Class and offers three common operations.

• A stack is a Last-In, First-Out (LIFO) abstract data type. The last value added to the stack will be the first value removed from the stack. My stack is implemented by a Stack Class and offers four common operations.

solution

---

queue____

• enqueue - Adds new value to the Queue.

• dequeue - Retrieves and removes value from Queue.

• is_empty - Returns True if the Queue is empty, othewise False.
• peek - Retrieves, but does not remove, value from Stack.

All these operations are performed in constant time, O(1). _ **stack**____

• push - Adds new value to the Stack.
• pop - Retrieves and removes value from Stack.
• peek - Retrieves, but does not remove, value from - Stack.
• is_empty - Returns True if Stack empty, othewise False.

All these operations are performed in constant time, O(1), by pushing and popping values from the head of the linked list.

---

Testing

• 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

---

Whiteboard Process