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README.md

Kotlin coding puzzles

This repository contains a set of programming puzzles that are solved using Kotlin language (hints, solutions tests and useful links are here as well). Purpose of this repository is to help you to practice coding and develop strong problem-solving skills. This will help you to become better programmer and improve you chance of getting a new job, by passing whiteboard coding interview.

Puzzle structure

Each puzzle is located in separate package and it contains of 3 main files (screen):

  • Puzzle.md - description of the task.
  • Puzzle.kt - empty method/class where puzzle should be solved. This file also contains helper methods and a set of JUnit tests which verifies if task was solved correctly.
  • PuzzleSolution.kt - file that contains one or more solutions.

Keep in mind that each puzzle will usually have more than one solution. Even simple puzzle like String reversal can be solved in 10 different ways. Usually, we compare various solutions using (Big O notation) to determine space/time complexity and we look at code readability.

How do I start?

  1. Checkout the and open the project
  2. Solve puzzle
  3. Run the tests

Let's solve some puzzles

Puzzles below are segregated by different difficulty. Repository also contains puzzles grouped by problem type and problem add order.

Some puzzle may contain a reference to other puzzles that should be solved before to have better understanding of the problem. To succeed you need to practice often, repeat same puzzles multiple times and be persistent over time. Take your time before you take a look at the presented solution. Good luck!

New in Town

Apprentice

Warrior

Commander

Useful links

More codding challenges

  • GeeksForGeeks - large and nicely segregated set of problems.
  • HackerRank - large set of problems and additional interview problems for business.
  • Project euler - more complex challenges, usually related to mathematics. Site already contains 600+ problems and a new code challenge is available very week or two. You will probably have to discuss problem with community because solutions are not on the website.
  • Advent of code - one month of various programing problems released daily at the end of the year. Fortunately archive of past events is still there.
  • Code Google Com Codejam - Google Code Jam, calls on programmers around the world to solve challenging, algorithmic puzzles against the clock. They publish all the past problems on their website.
  • CoderByte - 200+ challenges, data structures / algorithms / company interview problems segregated by difficulty. Unfortunately most of them is only available for premium users. Premium gives you access to premium step-by-step solutions and user solutions.
  • CodeChef - contains set of programming problems segregated by difficulty.
  • LeetCode - data structures / algorithms / company interview problems segregated by difficulty.
  • Code Forces - list of programming puzzles is smaller than other websites, but you will still have plenty problems to solve.
  • Spoj - list of programming puzzles is smaller than other websites, but you will still have plenty problems to solve.

Video courses

Books

Websites

  • Hiring without whiteboards - listing of companies (or teams) that don't do "whiteboard" interviews.
  • VisuAlgo - visualizes data structures and algorithms through animations algorithms.
  • Data structures explained - description of various data structures.
  • Sorting algorithms animations - visually compares most popular sorting algorithms using animations.
  • Big-O Reference - summarizes the complexities in terms of space and time (Big-O) of the most important algorithms and operations in common data structures.
  • Big-O poster - time/space complexity poster to print ant put on the wall.
  • Big-O Cheat Sheet - covers the space and time Big-O complexities of common algorithms.

Coding interview repositories

Contribute

If you think something is incorrect, have a better solution, give feedback or simply you want to add new coding puzzle just create PR or open a new issue.

Contributors

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