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

Sorted array with binary search

Answer

Nested loops with early exit

Answer

Priority queue

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

Store all visited node references in a hash set

Answer

Reverse the list and compare

Answer

Count nodes and traverse twice

Question 3

Which time complexity best describes an optimized merge sort implementation?

Accepted Answer

O(n log n)

Answer

O(n²)

Answer

O(n)

Answer

O(log n)

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

Level-order traversal storing all paths

Answer

Convert BST to sorted array first

Answer

Inorder traversal with parent pointers

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

O(n·k)

Answer

O(n log n)

Answer

O(k²)

Question 6

When solving a CodeSignal problem that requires generating all permutations of a string, which algorithmic paradigm is most commonly used?

Accepted Answer

Backtracking with swapping

Answer

Dynamic programming with memoization

Answer

Greedy selection

Answer

Divide and conquer merge

Question 7

In CodeSignal's General Coding Assessment, which of the following best describes a 'greedy' algorithm?

Accepted Answer

It makes the locally optimal choice at each step hoping to reach a global optimum

Answer

It tries all possible solutions and returns the best

Answer

It divides the problem into overlapping subproblems

Answer

It uses randomization to approximate the solution