CodeSignal Technical Assessment Array and String Manipulation 3

Question 1

What is the output of [x**2 for x in range(5) if x % 2 == 0]?

Accepted Answer

[0, 4, 16]

Answer

Even values in range(5) are 0, 2, 4; squaring them yields [0, 4, 16].

Question 2

Which data structure most efficiently supports O(1) duplicate detection while building a result array from an input array?

Accepted Answer

Hash set

Answer

A hash set provides O(1) average-case membership checks, making it ideal for tracking seen elements during a single pass.

Question 3

Given array [5, 3, 8, 1, 9, 2, 7], how many comparisons does binary search make to find 7 (assuming the array is first sorted)?

Accepted Answer

3

Answer

Sorted array is [1,2,3,5,7,8,9]; binary search checks index 3 (5), then index 5 (8), then index 4 (7) — 3 comparisons.

Question 4

What does ''.join(reversed('hello')) return?

Accepted Answer

'olleh'

Answer

reversed() yields characters in reverse order, and ''.join() concatenates them into the string 'olleh'.

Question 5

What is the space complexity of an in-place array reversal algorithm?

Accepted Answer

O(1)

Answer

In-place reversal swaps elements using a constant number of temporary variables regardless of array size.

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