Data Structure Questions and Answers – Queue Operations.

This set of Data Structure Multiple Choice Questions & Answers (MCQs) focuses on “Queue Operations”.

**1. A linear list of elements in which deletion can be done from one end (front) and insertion can take place only at the other end (rear) is known as _____________**a) Queue

b) Stack

c) Tree

d) Linked list

**Answer: a**Explanation: Linear list of elements in which deletion is done at the front side and insertion at the rear side is called Queue. In stack, we will delete the last entered element first.

**2. The data structure required for Breadth-First Traversal on a graph is?**a) Stack

b) Array

c) Queue

d) Tree

**Answer: c**Explanation: In Breadth-First Search Traversal, BFS, starting vertex is first taken and adjacent vertices which are unvisited are also taken. Again, the first vertex which was added as an unvisited adjacent vertex list will be considered to add further unvisited vertices of the graph. To get the first unvisited vertex we need to follow the First In First Out principle. Queue uses the FIFO principle.

**3. A queue follows __________**a) FIFO (First In First Out) principle

b) LIFO (Last In First Out) principle

c) Ordered array

d) Linear tree

**Answer: a**Explanation: The element first added in the queue will be deleted first which is the FIFO principle.

**4. Circular Queue is also known as ________**a) Ring Buffer

b) Square Buffer

c) Rectangle Buffer

d) Curve Buffer

**Answer: a**Explanation: Circular Queue is also called a Ring Buffer. A circular Queue is a linear data structure in which the last position is connected back to the first position to make a circle. It forms a ring structure.

**5. If the elements “A”, “B”, “C”, and “D” are placed in a queue and are deleted one at a time, in what order will they be removed?**a) ABCD

b) DCBA

c) DCAB

d) ABDC

**Answer: a**Explanation: Queue follows FIFO approach. i.e. First in First Out Approach. So, the order of removal elements are ABCD.

**6. A data structure in which elements can be inserted or deleted at/from both ends but not in the middle is?**a) Queue

b) Circular queue

c) Dequeue

d) Priority queue

**Answer: c**Explanation: In dequeuer, we can insert or delete elements from both ends. In the queue, we will follow the first in first out principle for insertion and deletion of elements. Element with the least priority will be deleted in a priority queue.

**7. A normal queue, if implemented using an array of size MAX_SIZE, gets full when?**a) Rear = MAX_SIZE – 1

b) Front = (rear + 1)mod MAX_SIZE

c) Front = rear + 1

d) Rear = front

**Answer: a**Explanation: When Rear = MAX_SIZE – 1, there will be no space left for the elements to be added to the queue. Thus queue becomes full.

**8. Queues serve major role in ______________**a) Simulation of recursion

b) Simulation of arbitrary linked list

c) Simulation of limited resource allocation

d) Simulation of heapsort

**Answer: c**Explanation: Simulation of recursion uses the stack data structure. Simulation of arbitrary linked lists uses linked lists. Simulation of resource allocation uses queue as first entered data needs to be given first priority during resource allocation. Simulation of heap sort uses the heap data structure.

**9. Which of the following is not the type of queue?**a) Ordinary queue

b) Single-ended queue

c) Circular queue

d) Priority queue

Answer: b

Explanation: Queue always has two ends. So, the single-ended queue is not the type of queue.