If you want to get better at Data Structures and Algorithms (DSA), solving dsa mcq questions for quick concept revision is a great way to practice. These questions help you check what you’ve learned and find out where you need more work. They cover all the main topics like arrays, stacks, queues, trees, and sorting. In this article, you’ll get a helpful set of MCQs that will make your DSA preparation easier and more effective. Whether you’re a student or preparing for interviews, these questions can boost your skills step by step.
DSA Mcq Questions Set
- Which data structure uses LIFO order?
a) Queue
b) Stack
c) Array
d) Linked List
Answer: b) Stack
- What is the time complexity of inserting an element at the beginning of an array?
a) O(1)
b) O(n)
c) O(log n)
d) O(n log n)
Answer: b) O(n)
- Which of the following is a linear data structure?
a) Tree
b) Graph
c) Array
d) Hash Table
Answer: c) Array
- In a circular linked list, the last node points to:
a) Null
b) First node
c) Middle node
d) Itself
Answer: b) First node
- Which sorting algorithm has the best average-case time complexity?
a) Bubble Sort
b) Insertion Sort
c) Merge Sort
d) Selection Sort
Answer: c) Merge Sort
- What is the worst-case time complexity of Quick Sort?
a) O(n)
b) O(n log n)
c) O(n²)
d) O(log n)
Answer: c) O(n²)
- Which data structure is used for implementing recursion?
a) Queue
b) Stack
c) Heap
d) Array
Answer: b) Stack
- In a binary search tree, which traversal yields the elements in sorted order?
a) Pre-order
b) In-order
c) Post-order
d) Level-order
Answer: b) In-order
- Which of the following is not a self-balancing binary search tree?
a) AVL Tree
b) Red-Black Tree
c) B-Tree
d) Binary Search Tree
Answer: d) Binary Search Tree
- What is the space complexity of Breadth-First Search (BFS)?
a) O(1)
b) O(n)
c) O(log n)
d) O(n²)
Answer: b) O(n)
10. Which data structure is used in implementing LRU cache?
a) Stack
b) Queue
c) Hash Map with Doubly Linked List
d) Binary Search Tree
Answer: c) Hash Map with Doubly Linked List
- Which of the following operations is not O(1) in a hash table?
a) Insertion
b) Deletion
c) Searching
d) Traversing
Answer: d) Traversing
- What is the height of a complete binary tree with n nodes?
a) O(n)
b) O(log n)
c) O(n log n)
d) O(1)
Answer: b) O(log n)
- Which data structure is ideal for implementing a priority queue?
a) Stack
b) Queue
c) Heap
d) Linked List
Answer: c) Heap
- In which data structure are elements added at one end and removed from the other?
a) Stack
b) Queue
c) Deque
d) Array
Answer: b) Queue
- Which of the following is not a characteristic of a linked list?
a) Dynamic size
b) Random access
c) Efficient insertion/deletion
d) Sequential access
Answer: b) Random access
- Which algorithm is used to find the shortest path in a weighted graph?
a) DFS
b) BFS
c) Dijkstra’s Algorithm
d) Kruskal’s Algorithm
Answer: c) Dijkstra’s Algorithm
- In a min-heap, the value of each node is:
a) Greater than or equal to its parent
b) Less than or equal to its parent
c) Greater than or equal to its children
d) Less than or equal to its children
Answer: d) Less than or equal to its children
- Which data structure is used in graph adjacency list representation?
a) Array
b) Linked List
c) Stack
d) Queue
Answer: b) Linked List
- Which traversal uses a queue?
a) DFS
b) BFS
c) In-order
d) Pre-order
Answer: b) BFS
20.Which data structure supports insertion and deletion at both ends? a) Queue
b) Stack
c) Deque
d) Heap
Answer: c) Deque
- Time complexity for searching in a balanced BST is:
a) O(1)
b) O(log n)
c) O(n)
d) O(n log n)
Answer: b) O(log n)
- Which is true about a doubly linked list?
a) Has one pointer per node
b) Traversed in both directions
c) Uses less memory than singly linked list
d) Insertion is harder
Answer: b) Traversed in both directions
- Which in-place sorting algorithm has worst-case O(n²) complexity?
a) Merge Sort
b) Quick Sort
c) Heap Sort
d) Bubble Sort
Answer: d) Bubble Sort
- Which data structure is used for postfix evaluation?
a) Queue
b) Stack
c) Linked List
d) Array
Answer: b) Stack
- Max number of nodes in binary tree of height h?
a) 2h2^h2h
b) 2h+1−12^{h+1} – 12h+1−1
c) h2h^2h2
d) 2h+12h + 12h+1
Answer: b) 2h+1−12^{h+1} – 12h+1−1
25. Which algorithm detects cycles in graphs?
a) BFS
b) DFS
c) Prim’s
d) Kruskal’s
Answer: b) DFS
26. Best case for linear search?
a) O(n)
b) O(1)
c) O(log n)
d) O(n²)
Answer: b) O(1)
27. Which traversal visits all nodes level-wise?
a) In-order
b) Pre-order
c) Post-order
d) Level-order
Answer: d) Level-order
28. Fastest average case sorting algorithm for large data?
a) Merge Sort
b) Bubble Sort
c) Quick Sort
d) Insertion Sort
Answer: c) Quick Sort
- Which finds minimum spanning tree?
a) Floyd-Warshall
b) Kruskal’s
c) Dijkstra’s
d) Bellman-Ford
Answer: b) Kruskal’s
30.Which one is greedy?
a) DFS
b) Quick Sort
c) Prim’s Algorithm
d) Binary Search
Answer: c) Prim’s Algorithm
31. Most costly operation in singly linked list?
a) Insert at head
b) Delete from head
c) Traversal
d) Delete at tail
Answer: d) Delete at tail
32. Which allows both-end operations?
a) Stack
b) Queue
c) Deque
d) Heap
Answer: c) Deque
33. Which graph has no cycle?
a) Undirected
b) Directed
c) DAG
d) Weighted
Answer: c) DAG
34. Node with no children is called:
a) Root
b) Internal node
c) Leaf
d) Branch
Answer: c) Leaf
35. Worst-case insert time in heap?
a) O(n)
b) O(1)
c) O(log n)
d) O(n log n)
Answer: c) O(log n)
36. Which structure helps convert infix to postfix?
a) Queue
b) Stack
c) Array
d) Linked List
Answer: b) Stack
37. Which cannot be implemented with recursion?
a) Tower of Hanoi
b) DFS
c) Binary Search
d) Queue
Answer: d) Queue
38. Auxiliary space of Merge Sort:
a) O(n)
b) O(1)
c) O(log n)
d) O(n log n)
Answer: a) O(n)
39. Which one is non-linear?
a) Stack
b) Queue
c) Tree
d) Array
Answer: c) Tree
40. Null pointers in binary tree with n nodes?
a) n
b) n+1
c) n-1
d) 2n
Answer: b) n+1
41. Root → Left → Right is:
a) In-order
b) Post-order
c) Pre-order
d) Level-order
Answer: c) Pre-order
42. Best for graphs with negative weights?
a) Dijkstra
b) Bellman-Ford
c) BFS
d) Kruskal
Answer: b) Bellman-Ford
43. Best for undo in text editor?
a) Queue
b) Array
c) Stack
d) Tree
Answer: c) Stack
44. Height of skewed binary tree with n nodes?
a) log n
b) n
c) n/2
d) n-1
Answer: b) n
45. Backtracking problems like N-Queens use:
a) Stack
b) Queue
c) Tree
d) Graph
Answer: a) Stack
46. Function calls use:
a) Queue
b) Stack
c) Heap
d) Hash Table
Answer: b) Stack
47. Used in topological sorting:
a) DFS
b) BFS
c) Dijkstra
d) Kruskal
Answer: a) DFS
48. Max edges in undirected graph with n vertices:
a) n
b) n(n-1)/2
c) n²
d) n(n+1)/2
Answer: b) n(n-1)/2
49. Not needed in merge sort:
a) Recursion
b) Stack
c) Queue
d) Temp array
Answer: c) Queue
50. Divide-and-conquer algorithm:
a) Merge Sort
b) Bubble Sort
c) Insertion Sort
d) Selection Sort
Answer: a) Merge Sort
51. True about B-Trees:
a) Leaves on different levels
b) Supports binary search
c) Sorted format
d) O(n²) insertion
Answer: c) Sorted format
52. AVL insert/search/delete complexity:
a) O(n)
b) O(n²)
c) O(log n)
d) O(1)
Answer: c) O(log n)
53. DFS uses:
a) Queue
b) Stack
c) Linked List
d) Array
Answer: b) Stack
54. Uses hashing technique:
a) Stack
b) Graph
c) Hash Table
d) Heap
Answer: c) Hash Table
55. Best for sparse matrix representation:
a) Array
b) Linked List
c) Queue
d) Stack
Answer: b) Linked List
56. DFS uses which traversal?
a) In-order
b) Post-order
c) Pre-order
d) All of the above
Answer: d) All of the above
57. Best for bipartite graph check:
a) BFS
b) DFS
c) Kruskal
d) Prim
Answer: a) BFS
58. Sorting without recursion/stack:
a) Quick Sort
b) Merge Sort
c) Bubble Sort
d) Heap Sort
Answer: c) Bubble Sort
59. Which of the following data structures allows duplicate values?
a) Set
b) Map
c) Queue
d) HashSet
Answer: c) Queue
60. What does FIFO stand for in data structures?
a) Fast Input Fast Output
b) First In First Out
c) First In Fast Out
d) File In File Out
Answer: b) First In First Out
61. Which traversal is used to copy a binary tree?
a) In-order
b) Post-order
c) Pre-order
d) Level-order
Answer: c) Pre-order
62. Which sorting algorithm is stable?
a) Quick Sort
b) Selection Sort
c) Merge Sort
d) Heap Sort
Answer: c) Merge Sort
63. Which of the following is not a type of tree traversal?
a) In-order
b) Pre-order
c) Mid-order
d) Post-order
Answer: c) Mid-order
64. Which data structure is used in Breadth-First Search?
a) Stack
b) Queue
c) Heap
d) Graph
Answer: b) Queue
65. Which structure is best for implementing DFS iteratively?
a) Queue
b) Stack
c) Linked List
d) Tree
Answer: b) Stack
66. What is the maximum number of children a binary tree node can have?
a) 1
b) 2
c) 3
d) Unlimited
Answer: b) 2
67. Which algorithm is used to detect a cycle in a directed graph?
a) BFS
b) DFS with visited & recursion stack
c) Kruskal
d) Prim
Answer: b) DFS with visited & recursion stack
68. Which of the following has the highest space complexity?
a) Stack
b) Queue
c) Adjacency Matrix
d) Adjacency List
Answer: c) Adjacency Matrix
Wrapping Up
Practicing dsa mcq questions is one of the easiest ways to improve your DSA skills. They help you understand key topics better and quickly show you where you need more practice. Instead of just reading notes or watching videos, answering questions helps you stay active in your learning. It doesn’t take much time, and even solving a few daily can make a big difference. Whether you’re preparing for a test or an interview, MCQs are a smart way to stay on track. So keep going, stay consistent, and let every question teach you something new.
