stacks_and_queues
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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.
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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____
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enqueue - Adds new value to the Queue.
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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
 
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