1. CSE 214 – Computer Science II Stacks
Source:

2. What’s a stack? Anyone like PEZ? An ordered LIFO data structure
Last In First Out
How do they work?
stack data on top of each other
add data only to the top of the stack
take data only from the top of the stack
Anyone like PEZ?

3. Anatomy of a PEZ dispenser
Push
Push
Push
Pop
Pop
Pop
Ref:

4. Possible Implementations
How might we store our stack data?
in an array (we’ll do this in lecture)
in a linked list (you’ll do this in HW 5)

5. Using an array to store a Stack
Push
Push
Push
Pop
Pop
Pop

6. What array operations might we need?
Add element to end of array elements
push
Remove and get last element in array
pop
Examine last element in array
peek
Examine all the elements in array
iterator
Note: we may also have to periodically resize our array

7. Using a Linked List to store a Stack
head
null
head
null
head
null
head
null
head
null
head
null
head
null

8. What linked list operations might we need?
Append to end
push
Get from end
peek
Remove and get end
pop
Get all elements
stackIterator, hasNext, next
Bottom Line: Stacks can be efficiently implemented using a linked lists