Question 1

What is the time complexity of accessing an element in an array by index?

Accepted Answer

O(1). Array elements are stored contiguously in memory. Given the base address and index, any element is directly computed — O(1) access.

Question 2

Which data structure follows the LIFO principle?

Accepted Answer

Stack. Stack follows Last In, First Out (LIFO). The last element pushed is the first to be popped. Used in function call stacks, undo operations.

Question 3

What is the time complexity of binary search?

Accepted Answer

O(log n). Binary search halves the search space with each step on a sorted array. After k steps, n/2^k = 1, so k = log₂n — O(log n).

Question 4

What is the worst-case time complexity of QuickSort?

Accepted Answer

O(n²). QuickSort's worst case is O(n²) when the pivot is always the smallest or largest element (already sorted array). Average case is O(n log n).

Question 5

What is a singly linked list?

Accepted Answer

A sequence of nodes where each node points to the next. In a singly linked list, each node stores data and a pointer to the next node. The last node points to NULL. Traversal is one-directional.

Data Structures MCQ Quiz

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