CS245-2009S-04 Stacks and Queues 1
04-0: Abstract Data Types
•An Abstract Data Type is a definition of a type based on the operations that can be performed on it.
•An ADT is an interface
•Data in an ADT cannot be manipulated directly – only through operations defined in the interface
04-1: Abstract Data Types
•To define an ADT, give the operations that can be performed on it
•The ADT says nothing about how the operations are performed
•Could have different implementations of the same ADT
•First ADT for thie class: Stack
04-2: Stack
A Stack is a Last-In, First-Out (LIFO) data structure.
Stack Operations:
•Add an element to the top of the stack
•Remove the top element
•Check if the stack is empty
04-3: Stack Implementation
Array:
04-4: Stack Implementation
Array:
•Stack elements are stored in an array
•Top of the stack is the end of the array
•If the top of the stack was the beginning of the array, a push or pop would require moving all elements in
the array
•Push: data[top++] = elem
•Pop: elem = data[--top]
04-5: Stack Implementation
•See code & Visualizaion
04-6: Θ() For Stack Operations
Array Implementation:
push
pop
empty()
04-7: Θ() For Stack Operations
Array Implementation:
