Practice Data Structures MCQs with answers. Arrays, linked lists, trees, graphs, sorting & more — fully solved for GATE, NTS, interviews 2026. These MCQs are perfect for NTS, PPSC, FPSC, CSS, OTS, UPSC, GATE, UGC NET, bank exams, university exams, and job interviews. The bold green option ✅ is the correct answer.
Arrays & Linked Lists
1. An array stores elements in:
a) Random locations b) Contiguous memory locations ✅ c) Linked nodes d) Tree structure
2. Time complexity of accessing array element by index:
a) O(n) b) O(log n) c) O(1) ✅ d) O(n2)
3. A linked list consists of:
a) Arrays b) Nodes with data and pointer to next node ✅ c) Trees d) Graphs
4. Which data structure follows LIFO?
a) Queue b) Array c) Stack ✅ d) Linked List
Stacks & Queues
5. Stack operations are:
a) Enqueue Dequeue b) Push and Pop ✅ c) Insert Delete d) Get Set
6. A Queue follows:
a) LIFO b) FIFO (First In First Out) ✅ c) Random order d) LILO
7. Which operation adds element to a queue?
a) Push b) Pop c) Enqueue ✅ d) Dequeue
8. Recursion uses which data structure internally?
a) Queue b) Array c) Stack (call stack) ✅ d) Linked List
Trees & Graphs
9. The topmost node of a tree is called:
a) Leaf b) Child c) Root ✅ d) Parent
10. A binary tree has at most how many children per node?
a) 1 b) 2 ✅ c) 3 d) Unlimited
11. BFS stands for:
a) Binary First Search b) Breadth First Search ✅ c) Best First Search d) Balanced First Sort
Sorting Algorithms
12. Which sorting has best average time complexity?
a) Bubble Sort b) Selection Sort c) Merge Sort O(n log n) ✅ d) Insertion Sort
13. Bubble Sort worst-case complexity:
a) O(n) b) O(n log n) c) O(n2) ✅ d) O(1)
14. Which sorting divides array into halves recursively?
a) Bubble Sort b) Merge Sort ✅ c) Selection Sort d) Insertion Sort
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