How to use the DSA MCQ Quiz
- 1. Choose the length10 random DSA questions, or all 26.
- 2. AnswerTap an option. You see straight away whether it's right, with a one-line reason.
- 3. ReviewFinish to get your score and a list of every question with the correct answer.
Coverage
Questions span the topics that placement tests and technical interviews return to again and again:
- Arrays, searching and sorting: index access, inserting at the front, binary search, quicksort's worst case, merge sort's stability and space, and insertion sort's best case.
- Stacks, queues and linked lists: LIFO and FIFO, which one BFS and DFS use, reversing a list and Floyd's cycle detection.
- Trees and heaps: BST search, inorder traversal, tree height, heap insert and O(n) heapify.
- Hashing: average and worst-case lookups, and collisions.
- Graphs: Dijkstra, Bellman-Ford, minimum spanning trees and topological sort.
- Dynamic programming and techniques: overlapping subproblems, naive Fibonacci and two pointers.
A sample question explained
How long does it take to build a heap from n unsorted items with heapify? Many people answer O(n log n), because each insert costs O(log n). But bottom-up heapify is O(n). Half the nodes are leaves and don't move at all; a quarter move at most one level; and so on. The sum n/4·1 + n/8·2 + n/16·3 + … stays below n.
That kind of reasoning is what interviewers are really testing with Big-O questions. If an answer surprises you, read the explanation, then watch the algorithm in action with our visualizers, such as the heap visualizer and the sorting algorithm visualizer. Track problem practice with the DSA sheet tracker.
Frequently asked questions
Do I need to write code?
No. These are concept questions. For coding practice, use the JavaScript or Python practice problems.
Is Big-O worst case or average?
Each question says which case it means, for example quicksort's worst case or hash tables' average case.
Where are the questions from?
Uncodemy wrote them to cover common DSA interview topics.
Is the DSA MCQ quiz free to take?
Yes. The DSA MCQ quiz lets you answer every question with no form. At your first score screen we ask for your name and WhatsApp number once; after that, the DSA MCQ quiz and all other Uncodemy tools stay open.