CodeSignal Technical Assessment Array and String Manipulation 4

Question 1

What is the result of 'CodeSignal'.lower().replace('signal', 'test')?

Accepted Answer

'codetest'

Answer

lower() converts to 'codesignal', then replace('signal','test') substitutes 'signal' with 'test' → 'codetest'.

Question 2

Given a 2D matrix represented as a flat array with row-major order, what is the index of element at row r, column c in an n-column matrix?

Accepted Answer

r * n + c

Answer

Row-major layout stores row r starting at index r*n, so element (r, c) is at r*n + c.

Question 3

What is the minimum number of operations to convert 'kitten' to 'sitting' using edit distance (Levenshtein)?

Accepted Answer

3

Answer

kitten→sitten (substitute k→s), sitten→sittin (substitute e→i), sittin→sitting (insert g) = 3 operations.

Question 4

An array of 0s and 1s must be partitioned so all 0s come before all 1s. Which algorithm does this in O(n) with O(1) space?

Accepted Answer

Dutch National Flag (two-pointer partition)

Answer

Two pointers (left and right) swap misplaced elements until they meet, achieving O(n) time and O(1) extra space.

Question 5

What does 'abcabc'.count('abc') return?

Accepted Answer

2

Answer

Python's str.count() finds non-overlapping occurrences: 'abc' appears at index 0 and index 3 → returns 2.

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