Algorithms

Practice Exercises - Algorithms

Explore Algorithms Practice Exercises below. Choose a level and work through algorithm problems with worked solutions, from the fundamentals up to expert challenges.

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Algorithms
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About This Algorithm Test

These exercises have you design, implement, and analyze algorithms across sorting, graphs, and optimization.

These practice problems put algorithm design into action. You will implement and trace sorting algorithms like merge sort and quicksort, apply binary search and its variants, and solve problems with divide and conquer, greedy strategies, dynamic programming, and backtracking. Graph exercises use breadth first and depth first search, Dijkstra shortest paths, and minimum spanning tree algorithms. You will analyze each solution complexity in Big O and reason about correctness.

Optimization problems such as knapsack, longest common subsequence, and interval scheduling appear frequently. Each exercise asks you to select a technique, implement it correctly, and justify its efficiency, turning algorithmic knowledge into working, analyzable code. Applied algorithm skill is what coding interviews and real engineering both demand.

Sorting and searching underpin countless systems, graph algorithms route networks and rank results, and dynamic programming solves optimization in scheduling, bioinformatics, and resource allocation. Being able to recognize a problem pattern and implement the right technique quickly is the difference between a solution that scales and one that stalls.

Technology companies test this heavily because it reveals how a candidate reasons under constraints, and practicing implementation builds the fluency to move from problem statement to efficient, correct code, which is central to strong software engineering across nearly every domain. To prepare, implement the classic algorithms yourself and trace them on small inputs so their mechanics are concrete.

Practice spotting which paradigm a problem invites, then analyze the complexity of your solution as part of solving it. Study optimization problems repeatedly, since dynamic programming rewards recognizing overlapping subproblems. A strong score indicates that you can move from an unfamiliar problem to an efficient, correct implementation and defend its complexity.

That applied fluency is exactly what technical interviews reward and what engineering roles require whenever performance and scalability genuinely matter to the software you build.

What You Will Practice

Sorting and Searching

Implement and trace merge sort, quicksort, and binary search, comparing their behavior and complexity on different inputs.

Dynamic Programming

Solve optimization problems like knapsack and longest common subsequence by identifying overlapping subproblems and optimal substructure.

Graph Algorithms

Apply breadth first and depth first search, Dijkstra shortest paths, and minimum spanning trees to connectivity and routing problems.

Complexity Analysis

Determine Big O time and space costs for your solutions and justify why one approach scales better than another.

Sample Questions

A few real questions from this test, with answers and explanations. Take the full test above for the complete set.

Dijkstra's algorithm fails to produce correct results when:

Answer: The graph contains negative edge weights

Dijkstra's algorithm assumes that once a node's shortest distance is finalized, it cannot be improved. Negative edge weights can violate this assumption, causing incorrect results. Use Bellman-Ford for graphs with negative weights.

The 0/1 Knapsack problem has a time complexity of:

Answer: O(n * W) where W is the capacity

The dynamic programming solution builds a table of size n x W, where n is the number of items and W is the knapsack capacity. Each cell is computed in O(1), giving O(n * W) total. Note this is pseudo-polynomial since W is not bounded by n.

What is the time complexity of the Floyd-Warshall algorithm?

Answer: O(V^3)

Floyd-Warshall uses three nested loops over all V vertices, giving O(V^3) time complexity. It computes shortest paths between all pairs of vertices using dynamic programming.

What is the lower bound for comparison-based sorting algorithms?

Answer: O(n log n)

Any comparison-based sorting algorithm must make at least O(n log n) comparisons in the worst case. This is proven by the decision tree model: with n! possible orderings, the tree needs height log(n!) = O(n log n).

Amortized analysis is used to:

Answer: Find the average cost per operation over a sequence of operations

Amortized analysis determines the average performance of each operation in a worst-case sequence. For example, a dynamic array's append is O(1) amortized even though individual resizes cost O(n), because resizes happen infrequently.

Frequently Asked Questions

Find answers to common questions about this assessment

Look for a problem where a solution builds from solutions to smaller overlapping subproblems and where greedy choices can fail. Signs include asking for an optimal count, minimum, or maximum over combinations, as in knapsack or longest common subsequence. If brute force recomputes the same subproblems, dynamic programming applies.

Both run in average logarithmic linear time, but quicksort sorts in place with good cache locality and small constants, so it often runs faster in practice. Merge sort needs extra memory but guarantees its worst case bound and stability. The best choice depends on memory constraints and whether stability matters.

Dijkstra algorithm grows a set of nodes with known shortest distances, repeatedly selecting the nearest unvisited node and relaxing its edges to update neighbor distances. Using a priority queue makes this efficient. It finds shortest paths from a source in graphs with non negative edge weights reliably.

Analyze complexity before and during coding. Estimating cost upfront helps you reject approaches that will not scale before investing time in them. Confirming the analysis as you implement ensures the code matches your intended efficiency. In interviews, stating complexity while solving demonstrates the reasoning employers want to see.

Scores are based on the number of correct answers divided by total questions, with a breakdown by topic category.

Yes, questions are randomly selected and ordered from our question bank to ensure each attempt is unique.

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There is no pass/fail threshold. The test measures your knowledge level and provides detailed feedback for improvement.

For knowledge tests, we recommend answering without external help to get an accurate assessment. Practice exercises are designed for learning, so references are acceptable.

Our questions are written for structured educational practice and can give a useful snapshot of your current knowledge in the tested topics.

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