Stacks and Queues

Not really data structures – More of an enforcement of policy – Can be implemented using an array or linked list – Can store just about any kind of data Queues – First In, First Out (FIFO) – Like waiting in line Stacks – First In, Last Out (FILO) – Like a stack of trays Stacks and Queues

Stacks Three primary operations – Push() – put new data on the top of the stack – Pop() – remove data from the top of the stack – Peek() – get a copy of the data on the top of the stack Useful – our function stack! – stack of cards, tiles, loot, etc…

Example (pushing) 5 Note: could use a linked list also

Example (pushing) 5 11

Example (pushing)

Example (pushing)

Example (current stack)

Example (peeking)

Example (popping)

Example (pushing)

Example (popping)

Example (popping)

Example (popping) 5 11

Example (popping) 5 FILO

Queues Two primary operations – Enqueue() – put new data at the end of the queue – Dequeue() – remove data from the beginning of the queue – Peek() – yes, its still there… Useful – Enforcing fairness (waitlist at SPSU) – Player turns during a round

Example

Example (enqueue a 5) 5

Example 5

Example (enqueue an 11) 5 11

Example 511

Example (enqueue a -6)

Example

Example (dequeue)

Example (dequeue)

Example (dequeue) FIFO

Example (dequeue) 11 -6

Not really data structures – More of an enforcement of policy – Can be implemented using an array or linked list Queues are FIFO Stacks are FILO Which data structure is LILO? Which one is LIFO? Summary