Data Structures and Algorithms Exam
Questions And Correct Answers
(Verified Answers) Plus Rationales
2026 Q&A | Instant Download Pdf
1. Which data structure follows the Last-In, First-Out (LIFO)
principle?
A. Queue
B. Linked list
C. Stack
D. Heap
Answer: Stack
Rationale: A stack follows the Last-In, First-Out principle because the
most recently inserted element is the first element removed. Push
operations add elements to the top, while pop operations remove the
top element.
2. Which data structure follows the First-In, First-Out (FIFO)
principle?
A. Stack
B. Queue
C. Tree
D. Graph
Answer: Queue
,Rationale: A queue follows the First-In, First-Out principle. The
element that enters the queue first is normally the first element
removed, similar to a line of people waiting for service.
3. What is the typical time complexity of accessing an element by
index in an array?
A. O(log n)
B. O(n)
C. O(n log n)
D. O(1)
Answer: O(1)
Rationale: Arrays provide constant-time random access because the
memory address of an element can be calculated directly from its index
and the element size.
4. What is the worst-case time complexity of searching for an
arbitrary value in an unsorted array?
A. O(1)
B. O(log n)
C. O(n)
D. O(n log n)
Answer: O(n)
Rationale: In an unsorted array, the desired value may be located at
the final position or may not exist at all, requiring examination of
every element in the worst case.
5. Which operation inserts an element at the top of a stack?
A. Enqueue
B. Dequeue
,C. Push
D. Traverse
Answer: Push
Rationale: Push is the standard stack operation used to place a new
element at the top of the stack.
6. Which operation removes an element from the front of a queue?
A. Push
B. Dequeue
C. Pop
D. Insert
Answer: Dequeue
Rationale: Dequeue removes the element at the front of a queue,
preserving the FIFO behavior of the data structure.
7. Which data structure is generally most appropriate for
implementing recursive function calls?
A. Queue
B. Heap
C. Stack
D. Hash table
Answer: Stack
Rationale: Function calls are managed using a call stack. Each call
creates a stack frame containing information such as parameters,
local variables, and the return address.
8. What is the primary disadvantage of a singly linked list compared
with an array?
, A. It cannot store integers
B. It cannot grow dynamically
C. It does not provide direct constant-time indexed access
D. It always uses less memory
Answer: It does not provide direct constant-time indexed access
Rationale: A singly linked list requires traversal from the beginning to
reach a particular position, making indexed access O(n), whereas an
array normally provides O(1) indexed access.
9. In a singly linked list, what does the last node typically contain in
its next field?
A. The first node
B. A random address
C. The previous node
D. A null reference
Answer: A null reference
Rationale: The last node has no successor, so its next reference is
conventionally set to null or an equivalent sentinel value.
10. Which data structure is especially useful for representing
hierarchical relationships?
A. Stack
B. Queue
C. Tree
D. Array
Answer: Tree
Questions And Correct Answers
(Verified Answers) Plus Rationales
2026 Q&A | Instant Download Pdf
1. Which data structure follows the Last-In, First-Out (LIFO)
principle?
A. Queue
B. Linked list
C. Stack
D. Heap
Answer: Stack
Rationale: A stack follows the Last-In, First-Out principle because the
most recently inserted element is the first element removed. Push
operations add elements to the top, while pop operations remove the
top element.
2. Which data structure follows the First-In, First-Out (FIFO)
principle?
A. Stack
B. Queue
C. Tree
D. Graph
Answer: Queue
,Rationale: A queue follows the First-In, First-Out principle. The
element that enters the queue first is normally the first element
removed, similar to a line of people waiting for service.
3. What is the typical time complexity of accessing an element by
index in an array?
A. O(log n)
B. O(n)
C. O(n log n)
D. O(1)
Answer: O(1)
Rationale: Arrays provide constant-time random access because the
memory address of an element can be calculated directly from its index
and the element size.
4. What is the worst-case time complexity of searching for an
arbitrary value in an unsorted array?
A. O(1)
B. O(log n)
C. O(n)
D. O(n log n)
Answer: O(n)
Rationale: In an unsorted array, the desired value may be located at
the final position or may not exist at all, requiring examination of
every element in the worst case.
5. Which operation inserts an element at the top of a stack?
A. Enqueue
B. Dequeue
,C. Push
D. Traverse
Answer: Push
Rationale: Push is the standard stack operation used to place a new
element at the top of the stack.
6. Which operation removes an element from the front of a queue?
A. Push
B. Dequeue
C. Pop
D. Insert
Answer: Dequeue
Rationale: Dequeue removes the element at the front of a queue,
preserving the FIFO behavior of the data structure.
7. Which data structure is generally most appropriate for
implementing recursive function calls?
A. Queue
B. Heap
C. Stack
D. Hash table
Answer: Stack
Rationale: Function calls are managed using a call stack. Each call
creates a stack frame containing information such as parameters,
local variables, and the return address.
8. What is the primary disadvantage of a singly linked list compared
with an array?
, A. It cannot store integers
B. It cannot grow dynamically
C. It does not provide direct constant-time indexed access
D. It always uses less memory
Answer: It does not provide direct constant-time indexed access
Rationale: A singly linked list requires traversal from the beginning to
reach a particular position, making indexed access O(n), whereas an
array normally provides O(1) indexed access.
9. In a singly linked list, what does the last node typically contain in
its next field?
A. The first node
B. A random address
C. The previous node
D. A null reference
Answer: A null reference
Rationale: The last node has no successor, so its next reference is
conventionally set to null or an equivalent sentinel value.
10. Which data structure is especially useful for representing
hierarchical relationships?
A. Stack
B. Queue
C. Tree
D. Array
Answer: Tree
