For which of the following inputs does binary search take time O( n) in the worst case?

An array of n integers in increasing order

An array of n integers in any order

A linked list of n integers in any order

An array of n integers in increasing order

A linked list of n integers in increasing order

GATE DA 2025 Q27: When does binary search run in O(log n)?

For which of the following inputs does binary search take time $O(\log n)$ in the worst case?

Try it: multiple select: one or more correct options

Select all correct options. No negative marking, no partial marks.

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Answer: C (official GATE 2025 final answer key)

Concept used: Binary search needs sorted input and constant-time access to the middle element.

First step: Ask two questions for each option: is the data sorted, and can you jump to the middle element in $O(1)$ time?

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Source: official GATE 2025 DA question paper and final answer key, organised by IIT Roorkee. Question paper · Answer key