Stacks and Queues in Data Structures
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Questions and Answers

What does the TOP variable represent in a stack?

  • The number of elements currently in the stack
  • The index of the bottom element in the stack
  • The maximum size of the stack
  • The location of the top element in the stack (correct)

Which operation is performed when an element is added to a stack?

  • Pop
  • Push (correct)
  • Peek
  • IsFull

What will the IsEmpty function return if TOP is -1?

  • False, indicating the stack is full
  • True, indicating the stack is empty (correct)
  • False, indicating the stack has elements
  • True, indicating the stack is not empty

In a stack, which element is accessed first when deleting elements?

<p>Top element (D)</p> Signup and view all the answers

What happens if a push operation is attempted on a full stack?

<p>An error message will be displayed and execution will terminate (D)</p> Signup and view all the answers

How is a stack represented in a linear array?

<p>Elements are stored sequentially, with access determined by the TOP variable (C)</p> Signup and view all the answers

What will be the value of TOP after initializing an empty stack?

<p>-1 (A)</p> Signup and view all the answers

What does the IsFull function check?

<p>If the stack has reached its maximum capacity (B)</p> Signup and view all the answers

What happens when the stack is full during a push operation?

<p>An error message is printed and execution terminates. (D)</p> Signup and view all the answers

Which condition indicates that the stack is empty?

<p>top == -1 (D)</p> Signup and view all the answers

In the dynamic array implementation of a stack, what is used to check if the stack is full?

<p>top &gt;= capacity-1 (C)</p> Signup and view all the answers

What does the pop() operation do in a stack?

<p>Removes an element from the top of the stack. (D)</p> Signup and view all the answers

What happens if an attempt is made to pop an element from an empty stack?

<p>The function returns a special value indicating the stack is empty. (D)</p> Signup and view all the answers

Which statement about stackFull() is true?

<p>It prints an error message and exits the program. (B)</p> Signup and view all the answers

What is the initial capacity of the stack in the dynamic array implementation?

<p>1 (D)</p> Signup and view all the answers

What is the role of MALLOC in the dynamic stack implementation?

<p>It allocates memory for the stack. (D)</p> Signup and view all the answers

What is the primary purpose of the queueFull function?

<p>To terminate execution when the queue is full (C)</p> Signup and view all the answers

Which of the following describes the main disadvantage of traditional queue implementation?

<p>Shifting an array when an item is deleted is time-consuming (C)</p> Signup and view all the answers

In a circular queue implementation, how is the front variable adjusted?

<p>It points one position counterclockwise from the front element (D)</p> Signup and view all the answers

What does the rear index indicate in a queue?

<p>The position where the next element will be added (D)</p> Signup and view all the answers

What happens when a queue reaches its maximum size using a traditional array?

<p>It generates an error message and terminates execution (B)</p> Signup and view all the answers

Why is the time complexity of queueFull considered O(MAX_QUEUE_SIZE)?

<p>Due to the maximum number of elements in the queue (A)</p> Signup and view all the answers

Which method is NOT typically used to overcome the drawbacks of a traditional queue?

<p>Shifting elements to the left (D)</p> Signup and view all the answers

What is the outcome when an element is deleted from a traditional queue?

<p>All elements are moved to the left (D)</p> Signup and view all the answers

What does FIFO stand for in the context of queues?

<p>First-In-First-Out (A)</p> Signup and view all the answers

What indicates that a queue is empty?

<p>FRONT = NULL (A)</p> Signup and view all the answers

What happens to the FRONT variable when an element is deleted from the queue?

<p>It increases by 1. (D)</p> Signup and view all the answers

What is the maximum size of the queue array defined in the queue implementation?

<p>100 (C)</p> Signup and view all the answers

What is the purpose of the IsFullQ function?

<p>To check if the queue has reached its maximum size. (C)</p> Signup and view all the answers

Which statement correctly describes the role of the REAR variable?

<p>It points to the empty position for the next insertion. (D)</p> Signup and view all the answers

What would the deleteq() function return when the queue is empty?

<p>An error message indicating the queue is empty. (D)</p> Signup and view all the answers

Which of the following is true regarding the addq function?

<p>It increments REAR and checks for queue size before adding. (B)</p> Signup and view all the answers

What defines a recursively defined function?

<p>It must refer to itself in its definition and have base values. (A)</p> Signup and view all the answers

Which statement accurately describes the factorial function?

<p>The factorial function is defined in terms of itself for values greater than 0. (A)</p> Signup and view all the answers

What is the return value of the factorial function when the input is 0?

<p>1 (B)</p> Signup and view all the answers

In the recursive procedure to calculate factorial, what happens during the second step?

<p>It calls itself with N - 1 as an argument. (A)</p> Signup and view all the answers

What is the significance of base values in a recursive function?

<p>They determine when the function should stop calling itself. (D)</p> Signup and view all the answers

Which procedure accurately describes the calculation of GCD using recursion?

<p>It sets GCD as N if M is divisible by N without a remainder. (A)</p> Signup and view all the answers

Which of the following can be a common misconception about recursive functions?

<p>They must utilize a for loop to work properly. (A)</p> Signup and view all the answers

When calculating N! recursively, what operation is performed after the call to itself?

<p>Multiply N by the result of the smaller factorial. (A)</p> Signup and view all the answers

What does a deque allow in terms of element manipulation?

<p>Elements can be added or removed at either end but not in the middle. (A)</p> Signup and view all the answers

In an input-restricted deque, what operation can be performed only at one end?

<p>Insertions (D)</p> Signup and view all the answers

What determines the processing order in a priority queue?

<p>The assigned priorities of the elements (C)</p> Signup and view all the answers

Which statement is true regarding a priority queue's elements with the same priority?

<p>They are processed according to the order in which they were added. (A)</p> Signup and view all the answers

What denotes an empty deque in terms of pointers?

<p>LEFT = NULL (A)</p> Signup and view all the answers

Which representation refers specifically to a priority queue?

<p>One-way list representation (C)</p> Signup and view all the answers

What happens to a lower priority element in a priority queue when a higher priority element is present?

<p>It is processed after the higher priority elements. (D)</p> Signup and view all the answers

What is the effect of doubling the capacity in a queue implementation?

<p>It allows more elements to be enqueued. (A)</p> Signup and view all the answers

Flashcards

Stack Data Structure

An ordered list where insertions and deletions occur at the same end, called the top.

LIFO (Last-In, First-Out)

The principle that the last element added to a stack is the first one removed.

Stack Implementation (Array)

Using an array to store stack elements, with variables 'TOP' and 'MAX_STACK_SIZE'

Stack Overflow

Error that occurs when trying to add an element to a full stack.

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IsEmpty (Stack)

Checking if a stack is empty (TOP = -1).

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IsFull (Stack)

Checking if a stack is full (TOP = MAX_STACK_SIZE -1).

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Push Operation (Stack)

Adding an element to the top of the stack.

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Pop Operation (Stack)

Removing an element from the top of the stack.

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Stack Push Operation

Adds an element to the top of a stack. If the stack is full, it prints an error and exits.

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Stack Pop Operation

Removes and returns the element from the top of a stack, treating the stack like a LIFO structure

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Stack Full Condition

A condition when a stack's capacity is reached, preventing further elements from being added.

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Stack Empty Condition

A condition when a stack has no elements.

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Dynamic Array Implementation of Stack

A stack implementation where the array size adapts as needed, making the capacity adjustable.

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Stack Creation (using dynamic arrays)

Allocates memory for a stack using dynamic allocation, initialising its capacity to 1.

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IsEmpty Function for a Stack

Checks if a stack is empty (no elements present).

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IsFull Function for a Stack

Checks if a stack is full (no more space for adding elements).

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Recursive Function

A function that calls itself within its own definition.

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Well-Defined Recursive Function

A recursive function that has a base case (no self-reference) and each recursive call gets closer to the base case.

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Base Case (Recursive)

A specific input value for which a recursive function does not call itself.

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Factorial

The product of all positive integers from 1 up to a given positive integer (n).

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Factorial Function (Recursive)

A recursive function that calculates the factorial of a given positive integer using the formula: n! = n * (n-1)! where 0!=1.

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GCD

The greatest common divisor of two integers. It's the largest integer that divides both without a remainder.

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Recursive GCD

A recursive function to find the Greatest Common Divisor (GCD) of two numbers using a self-referencing approach.

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Iterative approach

A method of solving a problem by performing a series of steps sequentially, one by one.

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Queue

A linear data structure where elements are added at the rear and removed from the front (FIFO - First-In, First-Out).

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FIFO

The principle that the first element added to a queue is the first one removed.

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Queue Representation

Queues can be implemented using arrays or linked lists.

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Queue Operations

The functions (addq, deleteq, isEmptyQ, isFullQ) used to interact with a queue (to add, remove, check emptiness and fullness).

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queueFull() function

A function that prints an error message and exits the program if a queue is full.

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addq(item)

Adds an element (item) to the rear of the queue.

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deleteq()

Removes and returns the element from the front of the queue.

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Job Scheduling using Queues

Operating systems often use queues to process jobs. Jobs are processed in the order of arrival, unless priority is applied.

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Queue Drawback (Sequential)

When items are added and removed from a sequential queue, the queue shifts. This potentially leaves empty space at the front but still results in queueFull if the rear reaches maximum possible size.

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isEmptyQ

Checks if the queue is empty.

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isFullQ

Checks if the queue is full.

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Time Complexity of shifting queue

Moving the entire queue in a sequential queue has a worst case time complexity of O(MAX_QUEUE_SIZE).

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Circular Queue

A queue implementation avoids queue shifting by wrapping around the array. This keeps efficient memory use.

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Circular Queue - Front

In a circular queue, the front variable points one position before the front element's location.

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Circular Queue - Rear

In a circular queue, the rear variable is handled normally; it points to the last element.

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Circular Queue Wrapping

A data structure that wraps around the array end in a sequential fashion.

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Deque

A linear data structure that allows elements to be added and removed from both ends (front and rear).

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Input-restricted deque

A deque that allows insertions only at one end and deletions at both ends.

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Output-restricted deque

A deque that allows deletions only at one end and insertions at both ends.

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Priority Queue

A data structure which prioritizes elements based on their value, processing higher priority elements first.

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Priority Queue (one-way list)

A priority queue representation that uses a linearly connected structure where each item stores not just data but also its priority.

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Queue Full

A condition where a queue has reached its maximum capacity and cannot accept further elements.

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Circular Array

A data structure that stores data in a sequential manner, with the last and the first element considered to be adjacent.

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Dynamic Array

A technique used to adjust the capacity of an array as needed, during runtime.

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Study Notes

Stacks and Queues

  • A stack is an ordered list where insertions and deletions occur at one end, called the top.
  • Last-In-First-Out (LIFO)
  • Elements are added and removed from the top.
  • The first element inserted is the last to be removed.

Array Representation of Stacks

  • Stacks can be represented using a linear array.
  • Two variables are used: TOP and MAX_STACK_SIZE.
  • TOP holds the location of the top element.
  • MAX_STACK_SIZE specifies the maximum capacity.
  • TOP = -1 indicates an empty stack.

Stack Operations

  • Stack Create: Initializes a stack.
    • MAX_STACK_SIZE is often defined as a constant.
  • IsEmpty(Stack): Checks if the stack is empty. Returns true if top < 0.
  • IsFull(Stack): Checks if the stack is full. Returns true if top >= MAX_STACK_SIZE -1.
  • Push(item): Adds an element to the stack.
    • If the stack is full, calls stackFull().
    • Otherwise, increments top and stores the item.
  • Pop(): Removes and returns the top element.
    • If the stack is empty, returns stackEmpty().
    • Otherwise decrement top and return the element.
  • stackFull(): Handles the scenario if a stack is full.

Stacks using Dynamic Arrays

  • Stacks can also be implemented using dynamic arrays.
  • This allows the size of the stack to be adjusted during program execution.
  • REALLOC is often used for dynamic memory allocation.
  • capacity variable is used to track current size.

Stack Applications: Polish Notation

  • An expression is a sequence of operators and operands which evaluate to a single value.
  • Infix Expression: Operators are placed between operands. Ex: A + B
  • Prefix Expression (Polish Notation): Operators come before their operands. Ex: + AB
  • Postfix Expression (Reverse Polish Notation): Operators come after their operands. Ex: AB+

Evaluation of Postfix Expression

  • Evaluating a postfix expression is simpler than an infix expression.
  • Operands are pushed onto a stack.
  • When an operator is encountered, the required number of operands are popped, the operation is performed, and the result is pushed onto the stack.
  • The final result is at the top of the stack.

Recursion

  • A recursive procedure is one that calls itself directly or indirectly.
  • Criteria (base criteria) exist where the procedure does not call itself.
  • Each recursive call should move closer to the base criteria.

Factorial Function

  • The factorial of a non-negative integer n, denoted by n!, is the product of all positive integers from 1 to n.
  • 0! = 1
  • n! = n * (n-1)! (for n > 0)

Queues

  • A queue is an ordered list where insertions occur at one end(rear) and deletions occur at the other end (front).
  • First-In-First-Out (FIFO)
  • The first element added is the first element removed.

Queue Representation Using Arrays

  • QUEUE is a linear array.
  • FRONT points to the front element.
  • REAR points to the rear element.
  • FRONT=REAR when the queue is empty.

Queue Operations

  • Queue CreateQ(): Initializes a queue with maximum size.
  • IsEmptyQ(): Checks if the queue is empty. returns true if front == rear
  • IsFullQ(): Checks if the queue is full. Returns true if rear== MAX_QUEUE_SIZE-1
  • addq(item): Adds an item to the queue.
  • deleteQ(): Removes an item from the queue. Returns the item if successful; otherwise an error code.

Circular Queues

  • When the queue is full, but there is empty space at the beginning.
  • This issue is addressed by using a circular queue implementation.

Priority Queues

  • Elements in a priority queue are assigned a priority.
  • Elements with higher priority are processed before those with lower priority.
  • Elements with the same priority are processed in the order they were added to the queue.

Ackermann Function

  • Ackermann function is a recursive function with two arguments.
  • The function is defined recursively in terms of itself.

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Data Structures and Applications (15CS33) Module 2 (simplified) PDF

Description

This quiz covers essential concepts of stacks and queues, specifically focusing on stack operations and their array representation. Explore the key features, including LIFO behavior, and the functions that manipulate stack data structures. Test your understanding of how stacks are created and managed in computer programming.

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