DSA interview question

Largest Element in an Array

Easy · Algorithms · Topics: array, linear search

The problem

A weather station uploads the day's temperature readings as an array, and the dashboard shows the maximum temperature. It's the simplest array problem there is, which is exactly why it appears in first rounds: the interviewer wants to see a single clean pass, a correct starting value (a real element, not 0, since temperatures can be negative), and the judgement not to sort the whole array just to read one value.

Example: [1, 8, 7, 56, 90] → 90.

Function signature

int largestElement(const vector<int>& a);  // a is non-empty

Test cases

Input `a`	Output	Explanation
`[1, 8, 7, 56, 90]`	90
`[5, 5, 5]`	5	All equal
`[-3, -1, -7]`	-1	Starting from 0 would wrongly return 0
`[10]`	10	Single element
`[2147483647, -5]`	2147483647	INT_MAX is handled

(Confirm: the array has at least one element; values can be negative.)

How interviewers phrase it

"Find the largest element in an array."
A warm-up before "second largest element" or "find max and min with the fewest comparisons".

Clarifying questions to ask

Can the array be empty? What should be returned then?
Can values be negative?
Should I return the value or its index?

Follow-ups to expect

"Why not sort and take the last element?"
"What should max start at?"
"Can you find both max and min in fewer than 2n comparisons?"
"Is there a library function?"
"Complexity?"

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