CodeSignal Technical Assessment Array and String Manipulation 2

Question 1

Given an array [3, 1, 4, 1, 5, 9, 2, 6], what is the result of rotating it left by 3 positions?

Accepted Answer

[1, 5, 9, 2, 6, 3, 1, 4]

Answer

Left rotation by 3 moves the first 3 elements [3,1,4] to the end, leaving [1,5,9,2,6,3,1,4].

Question 2

Which algorithm finds the maximum subarray sum in O(n) time?

Accepted Answer

Kadane's Algorithm

Answer

Kadane's Algorithm iterates once through the array tracking the current and global maximum subarray sum in O(n) time.

Question 3

What does the following produce for s = 'abcde': s[1:4]?

Accepted Answer

'bcd'

Answer

Python slice s[1:4] extracts characters at indices 1, 2, 3 — giving 'bcd'; the end index is exclusive.

Question 4

What is the time complexity of checking whether two strings are anagrams by sorting both?

Accepted Answer

O(n log n)

Answer

Sorting each string takes O(n log n), which dominates the O(n) comparison step.

Question 5

An array contains integers 1–n with one duplicate and one missing value. Which approach finds both in O(n) time and O(1) space?

Accepted Answer

Use XOR and arithmetic sum/sum-of-squares formulas

Answer

XOR paired with arithmetic identities (expected sum and sum-of-squares vs actual) isolates both the duplicate and missing value in two passes without extra space.

Codesignal Practice Test

Codesignal Practice Test

CodeSignal Technical Assessment Array and String Manipulation 2