Data Structures and Algorithms - Old Questions

7. How stack as ADT? Explain with example.

A stack is an ordered collection of items into which new items may be inserted and from which items may be deleted at one end, called the top of the stack. The deletion and insertion in a stack is done from top of the stack.

 It is a linear data structure which store data temporarily to perform PUSH and POP operation in LIFO (Last-In-First-Out) sequence.

Fig::A stack containing items or elements

Stack as ADT

A stack of elements of type T is a finite sequence of elements of T together with the operations

• CreateEmptyStack(S): Create or make stack S be an empty stack
• Push(S, x): Insert x at one end of the stack, called its top
• Top(S): If stack S is not empty; then retrieve the element at its top
• Pop(S): If stack S is not empty; then delete the element at its top
•  IsFull(S): Determine if S is full or not. Return true if S is full stack; return false otherwise
• IsEmpty(S): Determine if S is empty or not. Return true if S is an empty stack; return false otherwise.

Thus by using a stack we can perform above operations thus a stack acts as an ADT.