**Introduction**

Hey Ninjas! We hope you are preparing well for the interviews. In this article, we are going to discuss the __Data Structure__ MCQs. If you are not familiar with Data structures, you might be facing very difficulties in your interview rounds. Having a good knowledge of Data structures and algorithms is very important not only from a placement point of view but also for solving real-world problems.

To help you in your preparation, we have curated a list of Data Structure MCQ questions according to their difficulty level. Letâ€™s discuss them with their explanations.

**Easy Data Structure MCQs**

### 1. Which data structure is used to perform level-order traversal on a binary tree?

**(a) Stack**

**(b) Linked List**

**(c) Queue**

**(d) Hash Table**

**Ans. **(c) Queue** **

**Explanation. **The Queue is based on the principle of FIFO ( First in first out ), so it is used to process all the elements at the same level at once.

### 2. What is the best and worst case time complexity for a quick sort algorithm?

**(a) Best case: O(1), Worst case: O(n*log(n))**

**(b) Best case: O(n), Worst case: O(n*log(n))**

**(c) Best case: O(n*log(n)), Worst case: O(n*log(n))**

**(d) Best case: O(n*log(n)), Worst case: O(n*n)**

**Ans. **(d)** **Best case: O(n*log(n)), Worst case: O(n*n)

**Explanation. **The best case occurs when we select the mean element as the pivot, and the worst case occurs when the array is already sorted and we select the smallest or largest indexed element as the pivot.

### 3. What is the minimum number of queues required for implementing a stack?

**(a) 1**

**(b) 2**

**(c) 3**

**(d) 4**

**Ans. **(b) 2

**Explanation.** We need to use 2 queues, one queue will enqueue the elements, and the second will be used to dequeue elements.

### 4. Which data structure is used to check a palindrome?

**(a) Linked List**

**(b) Stack**

**(c) Queue**

**(d) Tree**

**Ans. **(b) Stack

**Explanation. **Since stack works on the LIFO principle ( Last in first out ), we put elements till mid into the stack and compare them with the remaining elements.

### 5. Which of the following is the application of data structures?

**(a) Image processing**

**(b) Decision making**

**(c) **__Blockchain__

**(d) All of the above**

**Ans. **(d) All of the above

**Explanation. **The Data structure are used to store, organize, process, and retrieve data in an efficient manner; hence they can be used in all the above fields.

### 6. Which matrix among the following has lots of zero elements?

**(a) Identity matrix**

**(b) Zero matrix**

**(c) Unit matrix**

**(d) Sparse matrix**

**Ans. **(d) Sparse matrix

**Explanation. **A sparse matrix is a matrix that has the majority of zero elements.

### 7. What condition should be checked before the deletion operation from the Queue?

**(a) Front value**

**(b) Rear value**

**(c) Underflow**

**(d) Overflow**

**Ans. **(c) Underflow

**Explanation. **Underflow is the condition when there are no elements in the Queue. There should be a minimum of one element in the Queue if you want to perform a delete operation.

### 8. Which among the following data structures is used to implement a priority queue?

**(a) Array**

**(b) Tree**

**(c) Graph**

**(d) Heap**

**Ans. **(d) Heap

**Explanation. **We can implement a priority queue using the following data structures: list, array, BST, or heap. But the most efficient one is a heap.

### 9. What is an AVL tree?

**(a) A tree that has utmost two children**

**(b) A tree that has utmost three children**

**(c) A binary search tree and height-balanced tree**

**(d) A binary search tree but an unbalanced tree**

**Ans. **(c) A binary search tree and height-balanced tree

**Explanation. **An AVL tree is a binary search tree and the height-balanced tree.

### 10. Which algorithm is used for the 8 Queens problem?

**(a) Dynamic Programming**

**(b) Branch and bound**

**(c) Backtracking**

**(d) None of the above**

**Ans. **(c) Backtracking

**Explanation. **The backtracking algorithm searches every possible arrangement in which we can place the 8 queens. We have to check the different columns for each queen. There should not be any clashes in the column or any diagonal.

You can check out How to Solve __8 Queens Problem Using Backtracking__ here.