Coding Challenges and Practice Flashcards
7 cards from real CodeSignal Technical Assessment practice questions. Tap to flip, then mark Knew It or Still Learning ā missed cards come back until you master them.
Read the first 7 Coding Challenges and Practice flashcards as text
A CodeSignal problem asks for the shortest path in an unweighted graph. Which algorithm should you use?
Answer: Breadth-first search
BFS explores nodes level by level, guaranteeing the first time a node is reached is via the shortest path in an unweighted graph.
You need to compute the nth Fibonacci number efficiently using dynamic programming. What is the time and space complexity of the tabulation (bottom-up) approach?
Answer: O(n) time, O(1) space with two variables
Using only two rolling variables to store the previous two results gives O(n) time and O(1) space.
In a CodeSignal assessment, you're asked to check if a string is a palindrome ignoring non-alphanumeric characters. What is the most efficient approach?
Answer: Two-pointer technique from both ends
Two pointers starting at each end and skipping non-alphanumeric characters compare in O(n) time and O(1) space.
What distinguishes a stable sorting algorithm from an unstable one?
Answer: Stable sorts preserve the relative order of equal elements
A stable sort guarantees that records with equal keys appear in their original input order in the sorted output.
A CodeSignal problem requires computing the maximum profit from one buy-sell of a stock given daily prices. What algorithmic approach solves this in O(n)?
Answer: Track the running minimum buy price and maximum profit in one pass
One pass tracking the minimum price seen so far and updating max profit at each step achieves O(n) time and O(1) space.
In CodeSignal's framework, tasks are scored based on test cases passing. If your solution passes 8 of 10 test cases with O(nĀ²) complexity but fails on large inputs, what should you prioritize?
Answer: Optimize the algorithm to a lower time complexity
Failing on large inputs is a classic sign of a complexity bottleneck; improving the algorithm's time complexity will handle all valid inputs.
Which of the following problems is best solved using a monotonic stack?
Answer: Computing the next greater element for each position
A monotonic stack efficiently resolves 'next greater element' queries by popping elements that are smaller than the current one.