donnemartin/interactive-coding-challenges

interactive-coding-challenges

120+ continually updated, interactive, and test-driven coding challenges, with Anki flashcards.

Challenges focus on algorithms and data structures found in coding interviews.

Each challenge has one or more reference solutions that are:

• Fully functional
• Unit tested
• Easy-to-understand

Challenges will soon provide on-demand incremental hints to help you arrive at the optimal solution.

Notebooks also detail:

• Constraints
• Test cases
• Algorithms
• Big-O time and space complexities

Also included are unit tested reference implementations of various data structures and algorithms.

Challenge Solutions

Anki Flashcards: Coding and Design

The provided Anki flashcard deck uses spaced repetition to help you retain key concepts.

• Coding deck

Great for use while on-the-go.

Design Resource: The System Design Primer

Looking for resources to help you prep for the System Design and Object-Oriented Design interviews?

Check out the sister repo The System Design Primer, which contains additional Anki decks:

• System design deck
• System design exercises deck
• Object oriented design exercises deck

Notebook Structure

Each challenge has two notebooks, a challenge notebook with unit tests for you to solve and a solution notebook for reference.

Problem Statement

• States the problem to solve.

Constraints

• Describes any constraints or assumptions.

Test Cases

• Describes the general and edge test cases that will be evaluated in the unit test.

Algorithm

• [Challenge Notebook] Empty, refer to the solution notebook algorithm section if you need a hint.
• [Solution Notebook] One or more algorithm solution discussions, with Big-O time and space complexities.

Hints

• [Challenge Notebook] Provides on-demand incremental hints to help you arrive at the optimal solution. Coming soon!

Code (Challenge: Implement Me!)

• [Challenge Notebook] Skeleton code for you to implement.
• [Solution Notebook] One or more reference solutions.

Unit Test

• [Challenge Notebook] Unit test for your code. Expected to fail until you solve the challenge.
• [Solution Notebook] Unit test for the reference solution(s).

Index

Challenges Categories

Format: Challenge Category - Number of Challenges

• Arrays and Strings - 10
• Linked Lists - 8
• Stacks and Queues - 8
• Graphs and Trees - 21
• Sorting - 10
• Recursion and Dynamic Programming - 17
• Mathematics and Probability - 6
• Bit Manipulation - 8
• Online Judges - 16
• System Design - 8
• Object Oriented Design - 8

Total number of challenges: 120

Reference Implementations: Data Structures

Unit tested, fully functional implementations of the following data structures:

• Linked List
• Stack
• Queue
• Binary Search Tree
• Graph
• Min Heap
• Trie
• Priority Queue
• Hash Map

Reference Implementations: Algorithms

Unit tested, fully functional implementations of the following algorithms:

• Selection Sort
• Insertion Sort
• Quick Sort
• Merge Sort
• Radix Sort
• Topological Sort
• Tree Depth-First Search (Pre-, In-, Post-Order)
• Tree Breadth-First Search
• Graph Depth-First Search
• Graph Breadth-First Search
• Dijkstra's Shortest Path
• Unweighted Graph Shortest Path
• Knapsack 0/1
• Knapsack Unbounded
• Sieve of Eratosthenes

Reference Implementations: TODO

• A*
• Bellman-Ford
• Bloom Filter
• Convex Hull
• Fisher-Yates Shuffle
• Kruskal's
• Max Flow
• Prim's
• Rabin-Karp
• Traveling Salesman
• Union Find
• Contribute

Installing and Running Challenges

• Repo Structure
• Notebook Installation
• Running Challenges

Misc

• Contributing
• Credits
• Contact Info
• License

Challenges

Image Credits

Arrays and Strings

Linked Lists

Stacks and Queues

Graphs and Trees

Sorting

Recursion and Dynamic Programming

Mathematics and Probability

Bit Manipulation

Online Judges

Repo Structure

interactive-coding-challenges        # Repo
├─ arrays_strings                    # Category of challenges
│  ├─ rotation                       # Challenge folder
│  │  ├─ rotation_challenge.ipynb    # Challenge notebook
│  │  ├─ rotation_solution.ipynb     # Solution notebook
│  │  ├─ test_rotation.py            # Unit test*
│  ├─ compress
│  │  ├─ compress_challenge.ipynb
│  │  ├─ compress_solution.ipynb
│  │  ├─ test_compress.py
│  ├─ ...
├─ linked_lists
│  ├─ palindrome
│  │  └─ ...
│  ├─ ...
├─ ...

*The notebooks (.ipynb) read/write the associated unit test (.py) file.

Notebook Installation

Zero Install

This README contains links to Binder , which hosts dynamic notebooks of the repo's contents online with no installation needed.

Jupyter Notebook

Run:

pip install jupyter

For detailed instructions, scripts, and tools to more optimally set up your development environment, check out the dev-setup repo.

For more details on notebook installation, follow the directions here.

More information on IPython/Jupyter Notebooks can be found here.

Running Challenges

Notebooks

Challenges are provided in the form of IPython/Jupyter Notebooks and have been tested with Python 2.7 and Python 3.x.

If you need to install IPython/Jupyter Notebook, see the Notebook Installation section.

• This README contains links to nbviewer, which hosts static notebooks of the repo's contents
• To interact with or to modify elements within the dynamic notebooks, refer to the instructions below

Run the notebook of challenges:

$ git clone https://github.com/donnemartin/interactive-coding-challenges.git
$ cd interactive-coding-challenges
$ jupyter notebook

This will launch your web browser with the list of challenge categories:

• Navigate to the Challenge Notebook you wish to solve
• Run the cells within the challenge notebook (Cell->Run All)
  • This will result in an expected unit test error
• Solve the challenge and verify it passes the unit test
• Check out the accompanying Solution Notebook for further discussion

To debug your solution with pdb, refer to the following ticket.

Note: If your solution is different from those listed in the Solution Notebook, consider submitting a pull request so others can benefit from your work. Review the Contributing Guidelines for details.

Future Development

Challenges, solutions, and unit tests are presented in the form of IPython/Jupyter Notebooks.

• Notebooks currently contain mostly Python solutions (tested on both Python 2.7 and Python 3.x), but can be extended to include 40+ supported languages
• Repo will be continually updated with new solutions and challenges
• Contributions are welcome!

Contributing

Contributions are welcome!

Review the Contributing Guidelines for details on how to:

• Submit issues
• Add solutions to existing challenges
• Add new challenges

Credits

Resources

• Cracking the Coding Interview | GitHub Solutions
• Programming Interviews Exposed
• The Algorithm Design Manual | Solutions
• CareerCup
• Quora
• HackerRank
• LeetCode

Images

• Arrays and Strings: nltk.org
• Linked Lists: wikipedia.org
• Stacks: wikipedia.org
• Queues: wikipedia.org
• Sorting: wikipedia.org
• Recursion and Dynamic Programming: wikipedia.org
• Graphs and Trees: wikipedia.org
• Mathematics and Probability: wikipedia.org
• Bit Manipulation: wikipedia.org
• Online Judges: topcoder.com

Contact Info

Feel free to contact me to discuss any issues, questions, or comments.

My contact info can be found on my GitHub page.

License

I am providing code and resources in this repository to you under an open source license. Because this is my personal repository, the license you receive to my code and resources is from me and not my employer (Facebook).

Copyright 2015 Donne Martin

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.