# Data Structure Questions and Answers – Queue Operations

**1. 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

**Explanation:** The FIFO method is used in the queue. i.e. the “First in, First Out” strategy. As a result, the elements should be removed in the following order: ABCD.

**2. 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

**Explanation:** We can insert and delete elements from both ends in dequeuer. For insertion and deletion of elements in the queue, we will use the first in, first out principle. In a priority queue, the element with the lowest priority will be eliminated.

**3. 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

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

**4. Queues serve major role in ______________**

a) Simulation of recursion

b) Simulation of arbitrary linked list

**c) Simulation of limited resource allocation**

d) Simulation of heap sort

**Explanation:** The stack data structure is used to simulate recursion. Linked lists are used to represent arbitrary linked lists. Because the first entered data needs to be given first priority during resource allocation, simulations of resource allocation use queues. Heap data structure is used to simulate heap sort.

**5. Which of the following is not the type of queue?**

a) Ordinary queue

**b) Single ended queue**

c) Circular queue

d) Priority queue

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

**6. 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

**Explanation:** Queue is a linear list of elements in which deletion occurs at the front and addition occurs at the back. In stack, the last element entered will be deleted first.

**7. The data structure required for Breadth First Traversal on a graph is?**

a) Stack

b) Array

**c) Queue**

d) Tree

**Explanation:** BFS, or Breadth First Search Traversal, takes the initial vertex first, followed by nearby unvisited vertices. To add more unvisited vertices to the graph, the first vertex that was added as an unvisited neighbouring vertex list will be considered once again. The First In First Out principle must be followed to obtain the first unvisited vertex. The FIFO principle is used in the queue.

**8. A queue follows __________**

**a) FIFO (First In First Out) principle**

b) LIFO (Last In First Out) principle

c) Ordered array

d) Linear tree

**Explanation:** Element first added in queue will be deleted first which is FIFO principle.

**9. Circular Queue is also known as ________**

**a) Ring Buffer**

b) Square Buffer

c) Rectangle Buffer

d) Curve Buffer

**Explanation:** Ring Buffer is another name for Circular Queue. A circular queue is a linear data structure in which the initial and last positions are coupled to form a circle. It takes the shape of a ring.

Queue is a data structure that is similar to Stacks in that it is an abstract data structure. A queue, unlike stacks, is open on both ends. The one end is always used to input data (enqueue), while the other is always used to delete data (dequeue) (dequeue). The Initially-In-First-Out (FIFO) approach is used in Queue, which means that the data item that was stored first would be accessed first. On queue, the following four basic processes are generally performed: Enqueue: This command adds a new item to the queue. An overflow condition occurs when a queue is completely full. Removes an item from the queue by expansion project it. Ring Buffer is another name for Circular Queue. A circular queue is a linear data structure in which the initial and last positions are coupled to form a circle.