Welcome to the Linked List data structure quiz. This Linked List data structure quiz consists of 10+ multiple-choice questions (MCQ) with answers and explanations.

Remember, the goal here is to learn, so try answering each question before checking the answers and explanations.

# 1. What is a Linked List in data structure?

A) It is a linear data structure where each element is stored at a contiguous location and elements are accessed sequentially from the first element.
B) It is a type of data structure that consists of nodes, where each node contains a data field and a reference(link) to the next node in the sequence.
C) It is a non-linear data structure where each data element is connected to several other data elements in a hierarchical manner.
D) It is a special type of data structure that can be perceived as a complete binary tree.

B) It is a type of data structure that consists of nodes, where each node contains a data field and a reference(link) to the next node in the sequence.

## Explanation:

The Linked List is a sequential list of nodes, where each node is linked to the next one through a pointer/reference. This allows for efficient insertions and deletions. Options A, C, and D describe Array, Tree, and Heap data structures respectively.

# 2. What is a Doubly Linked List in data structure?

A) It is a type of linked list where each node contains a data field and two references, one to the next node and one to the previous node.
B) It is a type of linked list where each node contains a data field and a reference only to the next node.
C) It is a type of linked list where each node contains a data field and a reference only to the previous node.
D) It is a type of linked list where each node contains two data fields and a reference to the next node.

A) It is a type of linked list where each node contains a data field and two references, one to the next node and one to the previous node.

## Explanation:

A Doubly Linked List has nodes that each contain a data field and two references or links that point to the next and previous node in the sequence, respectively. This allows for traversing the list in both forward and backward directions. The other options incorrectly describe the structure of a doubly linked list.

# 3. In which scenario is the Linked List an excellent data structure?

A) When you need to insert elements at the end of the list
B) When you need to insert elements in the middle of the list
C) When you need to access elements in sequential order

B) When you need to insert elements in the middle of the list

## Explanation:

Linked List is excellent when it comes to the insertion and deletion of elements in the middle of the list as it can be done in constant time.

# 4. What is the time complexity of searching for an element in a Linked List?

A) O(1)
B) O(log n)
C) O(n)
D) O(n log n)

C) O(n)

## Explanation:

The time complexity for searching an element in a Linked List is O(n) as in the worst case we need to traverse through all the elements.

# 5. What is the primary advantage of a Circular Linked List over a Simple Linked List?

A) It uses less memory
B) It allows for O(1) insertions at the end of the list
C) It allows us to traverse the whole list starting from any node
D) It does not require a sentinel node

C) It allows us to traverse the whole list starting from any node

## Explanation:

The primary advantage of a circular linked list is that it allows us to traverse the entire list starting from any node. We can reach any node from any point.

# 6. In a Singly Linked List, what does the last node's next pointer point to?

A) The first node
B) The second last node
C) Null
D) Itself

C) Null

## Explanation:

In a Singly Linked List, the last node's next pointer points to null, indicating the end of the list.

# 7. In a Doubly Linked List, what does the first node's previous pointer point to?

A) The second node
B) The last node
C) Itself
D) Null

D) Null

## Explanation:

In a Doubly Linked List, the first node's previous pointer points to null.

# 8. Which of the following is not a type of Linked List?

## Explanation:

There is no balanced linked list. Balanced trees exist, but not balanced linked lists.

# 9. In which of the following scenarios is a Doubly Linked List most useful?

A) When we need to frequently add new elements
B) When we need to frequently delete elements
C) When we need to frequently traverse the list in both directions
D) When we need to frequently perform a binary search

C) When we need to frequently traverse the list in both directions

## Explanation:

A Doubly Linked List allows for efficient traversal in both directions.

# 10. How much extra memory does a doubly linked list need over a Singly Linked List per node?

A) 50% more
B) Twice as much
C) Depends on the size of the data
D) No extra memory is needed

A) 50% more

## Explanation:

In a doubly linked list, each node needs one extra pointer to store the address of the previous node, hence 50% more memory per node is needed compared to a singly linked list.

# 11. What is the time complexity to add a node at the beginning of the Linked List?

A) O(1)
B) O(log n)
C) O(n)
D) O(n log n)

A) O(1)

## Explanation:

The time complexity to add a node at the beginning of the Linked List is constant, O(1), because it involves only a couple of pointer updates.

# 12. What does a Linked List node not contain?

A) A pointer to the next node
B) A pointer to the previous node
C) Data
D) A pointer to the linked list

D) A pointer to the linked list

## Explanation:

Linked List node contains data and pointers to the next and (in the case of a doubly linked list) previous nodes. It does not have a pointer to the linked list itself.

# 13. Which of the following cannot be implemented efficiently using Linked List?

A) Stack
B) Queue
C) Priority Queue
D) Binary Search

D) Binary Search

## Explanation:

Binary search requires access to elements in the middle of the collection. This is not efficient in Linked List.

A) Dynamic size
B) Ease of insertion/deletion
C) Random access is not allowed
D) None of the above

C) Random access is not allowed

## Explanation:

A) It consumes more memory than a simple linked list
B) It is complex to implement
C) A simple loop through the list will never end
D) All of the above

C) A simple loop through the list will never end

## Explanation:

In a circular linked list, a loop running through the list will go indefinitely unless a stopping condition is implemented.

# 16. What is the main advantage of a linked list over an array?

A) Linked lists use less memory
B) Elements can be inserted in a linked list in O(1) time
C) Random access is more efficient in linked lists
D) Linked lists are easier to implement

B) Elements can be inserted in a linked list in O(1) time

## Explanation:

Insertion and deletion of a node in a Linked List is a constant time operation. It doesn't require shifting elements unlike in an array.

# 17. In a circular doubly linked list, what does the 'next' pointer of the last node point to?

A) The second last node
B) The first node
C) Null
D) Itself

B) The first node

## Explanation:

In a circular doubly linked list, the 'next' pointer of the last node points to the first node, and the 'previous' pointer of the first node points to the last node. This forms a circle.

# 18. What is the time complexity of a program that reverses a Linked List?

A) O(1)
B) O(n)
C) O(n^2)
D) O(log n)

B) O(n)

## Explanation:

To reverse a Linked List, one must traverse the entire list once. This results in a linear time complexity of O(n), where 'n' is the number of nodes in the LinkedList. The operation doesn't depend on any condition or nested operation, so there's no log(n) or n^2 complexity. It is also not a constant time operation, thus O(1) is not correct.

# 19. In which type of Linked List can traversals be performed in both directions?

D) None of the above

## Explanation:

In a Doubly Linked List, each node has a reference to both its next node and its previous node. This allows for bidirectional traversal, meaning you can move forwards or backward through the list. In contrast, a Singly Linked List only allows movement in one direction (forward), and a Circular Linked List is a variation of either singly or doubly linked lists where the last node points back to the first node (or to the first and last nodes in the case of a doubly circular linked list). However, the circularity does not by itself facilitate bidirectional traversal.

# 20. A Linked List in which none of the nodes contain a NULL pointer is referred to?

D) None of the above