CodeSignal Technical Assessment Coding Challenges and Practice 3

Question 1

A CodeSignal problem gives you a matrix and asks for the number of islands (connected groups of 1s). Which algorithm is best suited?

Accepted Answer

BFS or DFS flood-fill from each unvisited land cell

Answer

BFS or DFS starting from each unvisited '1' marks its entire island as visited, counting one island per launch.

Question 2

You are given an integer array and must return the length of the longest increasing subsequence (LIS). What is the time complexity of the optimal patience-sorting solution?

Accepted Answer

O(n log n)

Answer

Binary search on a maintained 'piles' array processes each element in O(log n), giving O(n log n) total.

Question 3

In a CodeSignal challenge, you must validate a set of parentheses including '(', ')', '{', '}', '[', ']'. Which structure is essential?

Accepted Answer

Stack (LIFO)

Answer

A stack's last-in-first-out behavior matches the requirement that the most recently opened bracket must be the next one closed.

Question 4

What does the space complexity O(1) mean in the context of an in-place sorting algorithm?

Accepted Answer

The algorithm uses a fixed amount of additional memory beyond the input

Answer

O(1) space means the algorithm's extra memory usage does not grow with the input size.

Question 5

A CodeSignal task requires implementing a min-heap. After inserting a new element, what operation restores the heap property?

Accepted Answer

Sift-up from the newly inserted position

Answer

Sift-up compares the new element with its parent and swaps upward until the heap property is restored.

Codesignal Practice Test

Codesignal Practice Test

CodeSignal Technical Assessment Coding Challenges and Practice 3