Queue and stacks

Queue and stacks

• 1.
  Queue and stacks • Whatthey are • How they work • How to make them • Typical problems
• 2.
  Sample exam question •What is a queue? • What is a stack? • How can one reverse the other?
• 3.
  Queue • First in •First Out FIFO
• 4.
  Stack • Last in •First out LIFO
• 5.
  The problem with queues •Queues work as you would expect – First in, First out - FIFO – Later items take their turn behind earlier ones. • Because of the ‘no shuffling’ rule, these turn out to be tricky to implement
• 6.
  Classic Array-Style Queue •Items are read off the front of the queue W H E R E sp T H E sp Front of Queue Rear of Queue Limit
• 7.
  Classic Array-Style Queue •And added to the rear W H E R E sp T H E sp S Front of Queue Rear of Queue Limit Item = W
• 8.
  Classic Array-Style Queue •Until we run out of space • Then we’re stuffed. W H E R E sp T H E sp S T R E Front of Queue Rear of Queue Limit Item = WHER Warning: Queue Full!
• 10.
  Brilliant Idea! • Ifyou get to the end .. • Wrap round to the front • Until you hit the Rear pointer E E T R E sp T H E sp S T R E Front of QueueRear of Queue Limit Item = WHERE
• 11.
  Circular queue • It’snot really a circle! E E T R E sp T H E sp S T R E Front of Queue Rear of Queue EndStart