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Questions and Answers
A print queue is an example of which abstract data structure?
A print queue is an example of which abstract data structure?
- Queue (correct)
- Stack
- Tree
- Linked List
What is the primary characteristic that distinguishes a queue from a stack?
What is the primary characteristic that distinguishes a queue from a stack?
- FIFO for queues, LIFO for stacks. (correct)
- Queues allow access to the last element, while stacks allow access to the first element.
- Queues use a single pointer, while stacks use two pointers.
- Stacks use dynamic memory allocation, while queues use static memory allocation.
In an array-based queue implementation, what is the purpose of using the modulo operator (%) when updating the rear pointer?
In an array-based queue implementation, what is the purpose of using the modulo operator (%) when updating the rear pointer?
- To dynamically resize the array when it becomes full.
- To handle wrap-around when the rear pointer reaches the end of the array. (correct)
- To ensure the rear pointer always points to the beginning of the array.
- To calculate the average value of the elements in the queue.
Which of the following is a disadvantage of using an array to implement a queue?
Which of the following is a disadvantage of using an array to implement a queue?
In a linked list implementation of a queue, what happens to the rear pointer when the last element is dequeued?
In a linked list implementation of a queue, what happens to the rear pointer when the last element is dequeued?
What is the time complexity of the peek operation in a queue?
What is the time complexity of the peek operation in a queue?
Which of the following applications is NOT typically associated with queues?
Which of the following applications is NOT typically associated with queues?
In the provided C code for an array-based queue, what is the purpose of the size variable within the QUEUE struct?
In the provided C code for an array-based queue, what is the purpose of the size variable within the QUEUE struct?
Given the C code for a linked-list queue, when does the front and rear both point to NULL?
Given the C code for a linked-list queue, when does the front and rear both point to NULL?
What occurs if the enqueue operation is called on a full queue in the given array implementation?
What occurs if the enqueue operation is called on a full queue in the given array implementation?
Consider an array-based queue with MAX_SIZE = 5. If front = 2 and rear = 4, how many elements are currently in the queue?
Consider an array-based queue with MAX_SIZE = 5. If front = 2 and rear = 4, how many elements are currently in the queue?
For a linked list implementation of a queue, which operation requires dynamic memory allocation?
For a linked list implementation of a queue, which operation requires dynamic memory allocation?
What happens to the value returned by dequeue when the queue is empty?
What happens to the value returned by dequeue when the queue is empty?
Which of the following scenarios would benefit most from using a queue data structure?
Which of the following scenarios would benefit most from using a queue data structure?
How does the use of queues in Breadth-First Search (BFS) contribute to the algorithm's functionality?
How does the use of queues in Breadth-First Search (BFS) contribute to the algorithm's functionality?
What is a primary benefit of using a linked list over an array for implementing a queue?
What is a primary benefit of using a linked list over an array for implementing a queue?
In the context of queues, what does 'buffering' typically refer to?
In the context of queues, what does 'buffering' typically refer to?
Consider an array queue where front is ahead of rear (e.g., front = 3, rear = 1, with MAX_SIZE = 5). How would you calculate the number of elements in the queue?
Consider an array queue where front is ahead of rear (e.g., front = 3, rear = 1, with MAX_SIZE = 5). How would you calculate the number of elements in the queue?
Why is it necessary to set q->rear = NULL; after the last element is dequeued, within the linked list implementation?
Why is it necessary to set q->rear = NULL; after the last element is dequeued, within the linked list implementation?
Flashcards
Queue (FIFO)
Queue (FIFO)
A First-In-First-Out data structure where elements are added at the rear(enqueue) and removed from the front(dequeue).
Array Queue
Array Queue
An array-based queue that uses a circular arrangement with front and rear pointers to manage elements efficiently.
Linked List Queue
Linked List Queue
A queue implementation where each element is a node containing data and a pointer to the next node, managed through front and rear pointers.
Enqueue
Enqueue
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Dequeue
Dequeue
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Peek (Queue)
Peek (Queue)
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IsEmpty (Queue)
IsEmpty (Queue)
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Breadth-First Search (BFS)
Breadth-First Search (BFS)
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Study Notes
- Queues are a First-In-First-Out (FIFO) data structure
Queue Concept
- Elements are added to the rear (enqueue) and removed from the front (dequeue)
Implementations
- Queues can be implemented using arrays or linked lists
Array Queue
- Employs a circular array with front and rear pointers
- Offers efficient space utilization but has a fixed size
- Uses wrap-around via a modulo operation to manage the circular nature, expressed as
i = (i + 1) % size
Linked List Queue
- Uses a front pointer to indicate the first node and a rear pointer for the last node
- Provides dynamic sizing
- Requires more memory due to pointer overhead
Key Operations and Complexities
- Enqueue (add): O(1)
- Dequeue (remove): O(1)
- Peek (view front): O(1)
- IsEmpty: O(1)
Applications
- Utilized in Breadth-First Search (BFS)
- Used for job scheduling (e.g. print queue, task management)
- Facilitates resource sharing among multiple consumers
- Used in buffering applications (e.g. keyboard buffers, web server request queues)
Code Pattern for Array Queue
- The C code defines a
QUEUEstructure with an integer array, front and rear indices, and a size variable MAX_SIZEis defined as 100, setting the maximum number of elements the queue can holdinitialize: Initializes the queue by setting the front to 0, rear to -1, and size to 0isEmpty: Checks if the queue is empty by testing if the size is 0isFull: Checks if the queue is full by testing if the size equalsMAX_SIZEenqueue: Adds an element to the rear of the queue; if the queue is full, the operation returns; the rear index is incremented using moduloMAX_SIZEto achieve wrap-arounddequeue: Removes an element from the front of the queue; If the queue is empty, it returns -1; the front index is incremented using moduloMAX_SIZE
Code Pattern for Linked List Queue
- The C code defines a
NODEstructure for linked list nodes, containing an integerdataand a pointernext - A
QUEUEstructure is defined withfrontandrearpointers toNODEelements initialize: Initializes the queue by setting bothfrontandreartoNULLisEmpty: Determines if the queue is empty by checking iffrontisNULLenqueue: Allocates a new node, assigns the provided value, and appends it to the rear of the queue; If the queue is empty, the new node becomes both thefrontandreardequeue: Removes the node from the front of the queue; If the queue is empty, it returns -1; thefrontpointer is advanced to the next node; iffrontbecomesNULL,rearis also set toNULL; the memory of the dequeued node is released
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