CodeSignal Technical Assessment Coding Challenges and Practice 2

Question 1

In a CodeSignal challenge, you need to find all pairs in an array that sum to a target value. Which data structure gives the most efficient average-case solution?

Accepted Answer

Hash set for complement lookup

Answer

A hash set allows O(1) average-case lookup of each element's complement, giving O(n) overall time complexity.

Question 2

A CodeSignal task asks you to detect a cycle in a singly linked list. What is the space-optimal approach?

Accepted Answer

Floyd's tortoise-and-hare two-pointer algorithm

Answer

Floyd's cycle detection uses two pointers moving at different speeds, achieving O(1) space and O(n) time.

Question 3

Which time complexity best describes an optimized merge sort implementation?

Accepted Answer

O(n log n)

Answer

Merge sort divides the array in half each level (log n levels) and merges in O(n) per level, yielding O(n log n) overall.

Question 4

In a CodeSignal challenge involving a binary search tree, you must find the lowest common ancestor of two nodes. What traversal approach is most direct?

Accepted Answer

Exploit BST ordering: recurse left if both nodes are smaller, right if both are larger

Answer

BST ordering lets you navigate directly: if both target values are less than the current node go left, if both are greater go right, otherwise the current node is the LCA.

Question 5

A sliding window problem asks for the maximum sum of any subarray of size k. What is the time complexity of the optimal solution?

Accepted Answer

O(n)

Answer

The sliding window technique adds one element and removes one per step, processing each element exactly once for O(n) time.

Codesignal Practice Test

Codesignal Practice Test

CodeSignal Technical Assessment Coding Challenges and Practice 2