CodeSignal Technical Assessment Array and String Manipulation 5

Question 1

What is the result of sorted([3,1,4,1,5,9], key=lambda x: -x)?

Accepted Answer

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

Answer

Negating each value as the sort key sorts in descending order, yielding [9, 5, 4, 3, 1, 1].

Question 2

Which string method splits 'one,two,,three' by comma and returns empty strings for consecutive delimiters?

Accepted Answer

'one,two,,three'.split(',')

Answer

str.split(',') treats each delimiter individually, preserving empty strings between consecutive commas → ['one','two','','three'].

Question 3

What is the worst-case time complexity of removing an element from the middle of a dynamic array (list)?

Accepted Answer

O(n)

Answer

Removing from the middle requires shifting all subsequent elements left by one, which is O(n) in the worst case.

Question 4

For the problem 'find the longest substring without repeating characters', which approach achieves O(n) time?

Accepted Answer

Sliding window with a hash set tracking current window characters

Answer

A sliding window expands the right pointer and shrinks the left pointer when a duplicate is found, processing each character at most twice → O(n).

Question 5

Given arrays A = [1, 3, 5] and B = [2, 4, 6], what is the median of the combined sorted array?

Accepted Answer

3.5

Answer

Combined sorted array is [1,2,3,4,5,6]; median of 6 elements is average of 3rd and 4th: (3+4)/2 = 3.5.

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