Cognizant Cognizant Data Structures and Algorithms

Question 1

What is the time complexity of binary search on a sorted array of n elements?

Accepted Answer

O(log n)

Answer

Binary search halves the search space each step, resulting in O(log n) time complexity.

Question 2

Which data structure uses LIFO (Last In, First Out) order?

Accepted Answer

Stack

Answer

A stack follows LIFO — the last element pushed is the first one popped.

Question 3

What is the worst-case time complexity of QuickSort?

Accepted Answer

O(n²)

Answer

QuickSort degrades to O(n²) when the pivot is always the smallest or largest element.

Question 4

Which traversal of a Binary Search Tree produces elements in sorted order?

Accepted Answer

In-order

Answer

In-order traversal (left → root → right) of a BST visits nodes in ascending sorted order.

Question 5

What data structure is best suited for implementing a BFS (Breadth-First Search)?

Accepted Answer

Queue

Answer

BFS processes nodes level by level using a FIFO queue to track nodes to visit next.

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