Queues and Stacks

1
Queues and Stacks

• Ryan Morris

2
Queues

• Queues are very simple FIFO (First In First Out)
  Data Types.
• Queues have two basic functions
• Enqueue (insert object into queue)
• Dequeue (remove object from queue)

3
Queues

• Enqueue simply inserts an object into the back of
  the queue. When objects are inserted they are
  placed in the back, unless the queue is empty
  then the back and the front elements are the same.

4
Queues

• Dequeue simply reverses the process by removing
  the front object (object inserted first) from the
  queue.

5
Queues

• Applications of queues
• Printer queues
• Socket queues
• File server queues
• Any real life line (first come first serve)

6
Queues

• Queues can be implemented with arrays or linked
  lists.

7
Queue

• Linked List representation

8
Queue

• Linked List representation after one dequeue

9
Stacks

• Stacks are slightly more complicated than queues
  for they are FILO (First In Last Out) data
  structures. Stacks generally have two main
  functions push, which inserts an object into the
  stack, and pop, which removes the top (or last
  pushed) object from the stack.

10
Stacks

• Here is a stack after a series of pushes

11
Stacks

• When popped the C would come first then the B
  then the A.

12
Stacks

• Applications of stacks include
• Balancing Symbols (such as parenthesis)
• Infix to Prefix notation conversion
• Postfix expression evaluation

13
Stack

• Linked List implementation

14
Stack

• Linked List representation after popping