Stacks

A stack is as the name says like a stack of paper. Meaning it follows the LIFO policy (last in first out). The most common operations on queues are:

• push(E e): Puts the element onto the top of the stack.
• E pop(): Takes the element from the top of the stack.
• E peek(): Returns the element at the top of the stack, which corresponds to the element to next be popped.

Implementing a Stack

// TODO

Stack Using two Queues

Although the most common way of implementing a stack is with a linked list it is also possible to implement a stack by using two queues. Just like when implementing a queue with two stacks you need to decide if adding or removing an element will be expensive.