Data Structures Unit 2: Stack & Queue

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Questions and Answers

What best describes a stack in terms of its data handling method?

Elements are managed in a first-in-first-out manner.

Elements can be added and removed from both ends.

Elements are accessed directly based on their index.

Elements can only be added and removed from one end, the top. (correct)

What happens when the TOP variable equals MAX-1 in a stack?

The stack can accommodate additional elements.

The stack is full and no further insertions can be made. (correct)

The stack needs to perform a pop operation.

The stack is empty and ready for new elements.

Which of the following operations does not belong to the basic operations of a stack?

Peek

Append (correct)

Push

Pop

In the array representation of a stack, what does a NULL value for TOP signify?

The stack is empty and no elements are present. Signup and view all the answers

When an attempt is made to insert an element into a full stack, what is the expected outcome?

An OVERFLOW message is printed. Signup and view all the answers

Which operation retrieves the topmost element without altering the stack?

Peek Signup and view all the answers

What data structure is NOT commonly used for implementing a stack?

Tree Signup and view all the answers

Which statement about stacks is true?

The last element added is the first one to be removed. Signup and view all the answers

What condition must be checked before performing a deletion operation on a stack?

Is TOP=NULL? Signup and view all the answers

What message is displayed when an attempt is made to delete from an empty stack?

UNDERFLOW Signup and view all the answers

What does the PEEK operation do in the context of a stack?

Returns the value of the element at a specified index. Signup and view all the answers

Before performing an update on a stack's element, what must be confirmed?

The stack is not empty. Signup and view all the answers

What best describes recursion in programming?

A process must have a termination condition. Signup and view all the answers

Which of the following is an example of a situation where recursion is used?

Calculating factorial numbers Signup and view all the answers

In a stack represented by a vector S and a pointer TOP, what does the I-th element from the top refer to?

Element at index TOP-I in vector S. Signup and view all the answers

Which recursive problem is NOT traditionally associated with recursion?

Bubble sort. Signup and view all the answers

Study Notes

Stack Overview

Stack is a linear data structure with a Last In First Out (LIFO) principle, where the last element added is the first to be removed.
Analogous to a pile of plates, elements can be added or removed only from the top position.

Implementation

Can be implemented using an array or a linked list.
Key variables:
- TOP: Stores the address of the top element.
- MAX: Indicates the maximum capacity of the stack.
- If TOP=NULL, the stack is empty; if TOP=MAX-1, the stack is full.

Operations on Stack

Four basic operations exist:
- Push: Adds an element to the top.
- Pop: Removes the top element.
- Peek: Retrieves the value of the top element without removing it.
- Update: Changes the value of an element at a specific index.

Push Operation

Adds a new element at the topmost position after checking if the stack is full (TOP=MAX-1).
If full, an "OVERFLOW" message is generated.

Pop Operation

Deletes the top element, ensuring the stack is not empty (TOP=NULL) before the operation.
If empty, an "UNDERFLOW" message is displayed.

Peek Operation

Returns the value of the element at a specified index from the top without deletion.

Update Operation

Changes the value of an element at a specified index, first checking if the stack is not empty.

Applications of Stack

Used in recursion where a function calls itself until a stopping condition is met.
Supports balancing symbols in expressions.
Utilized in Polish notations for expression evaluation.

Recursion

A process where a function repeatedly calls itself until a defined condition is fulfilled, preventing infinite loops.
Common examples include calculating factorials and generating Fibonacci sequences.

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Description

Explore the fundamental concepts of stack and queue in this quiz. Understand how these data structures operate, with practical examples like the analogy of a pile of plates for the stack. Test your knowledge on operations and characteristics associated with these essential structures in computer science.