## Data Structures Questions and Answers Part-4

1. What is the result of the following operation?
Top (Push (S, X))
a) X
b) X+S
c) S
d) XS

Answer: a
Explanation: The function Push(S,X) pushes the value X in the stack S. Top() function gives the value which entered last. X entered into stack S at last.

2. The prefix form of an infix expression (p + q) – (r * t) is?
a) + pq – *rt
b) – +pqr * t
c) – +pq * rt
d) – + * pqrt

Answer: c
Explanation: Given Infix Expression is ((p+q)-(r*t))
(+pq)-(r*t)
(-+pq)(r*t)
-+pq*rt

3. Which data structure is used for implementing recursion?
a) Queue
b) Stack
c) Array
d) List

Answer: b
Explanation: Stacks are used for the implementation of Recursion.

4. 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 front side and insertion at rear side is called Queue. In stack we will delete the last entered element first.

5. 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 follows First In First Out principle. Queue uses FIFO principle.

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

7. 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 as Ring Buffer. Circular Queue is a linear data structure in which last position is connected back to the first position to make a circle. It forms a ring structure.

8. 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.

9. 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 the ends. In queue, we will follow first in first out principle for insertion and deletion of elements. Element with least priority will be deleted in a priority queue.

10. 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 in queue. Thus queue becomes full.