stack.md

Stack

A LIFO (Last In, First Out) data structure.

Time Complexity

Operation	Big O
Push	O(1) amortized
Pop	O(1)
Peek	O(1)

Space complexity: O(n)

Pseudocode

Push

PUSH(stack, item):
    APPEND item to stack.items

Pop

POP(stack):
    IF stack.items is empty
        RETURN nil, false
    item = LAST element of stack.items
    REMOVE last element from stack.items
    RETURN item, true

Peek

PEEK(stack):
    IF stack.items is empty
        RETURN nil, false
    RETURN LAST element of stack.items, true