This is another take on 99 Scala Problems. However, the purpose of this is not to show how good I am solving them, but offering a way to beginners to practice and write their own solutions. This project will contain tests and the public interfaces of each problem, so anybody is free to implement solutions in their own way!
This 99 Scala problems are an adaptation of http://aperiodic.net/phil/scala/s-99/ which at it's turn are an adaptation of https://sites.google.com/site/prologsite/prolog-problems. I a couple of exercices to make them more testable.
The purpose of this exercercises is to practice and learn Scala, and using already built-in functions is discouraged.
I decided to start with this project because, long time ago, when I discovered the 99 Scala Problems, I had a lot of fun and I learned a lot about Scala. Recently, I stumbled upon them again, and I realized that there are no github projects (or at least, I couldn't find any) that could be used as a sandbox, where people can code their own solutions and run them against a battery of tests.
As in the original version, problems are in groupped in 7 different types: Lists, Arithmetic, Logic and Codes, Binary Trees, Multiway Trees, Graphs and Miscellaneous. Also the problems have different levels of difficulty marked by stars (*), being 1 star the easiest and 3 stars the most difficult ones.
It's easy, just pick a problem, read the tests, and implement the methods in the class. Some problems offer different alternatives to implement or interesting things to do, like adding your custom methods to Lists for example.
Each problem is located in the src folder under the corresponding package, so P01 is under com.github.jlprat.ninetynine.P01. Tests follow the same structure and are located under the test folder.
Once you are ready with your implementation open a terminal, go to the project folder and just run:
sbt test
Or if you want to run a specific test, for example P01 you can run:
sbt testOnly com.github.jlprat.ninetynine.p01.P01Spec
##Problem list
P01*: Find the last element of a list
P02*: Find the penultimate element of a list (last but one)
P03*: Find the kth element of a list
P04*: Find the number of elements of a list
P05*: Reverse a list
P06*: Find out if a list is a palindrome
P07**: Flatten a nested list structure
P08**: Eliminate consecutive duplicates of list elements
P09**: Pack consecutive duplicates of list elements into sublists
P10*: Run-length encoding of a list (Consecutive duplicates of elements are encoded as tuples (N, E) where N is the number of duplicates of the element E)
P11*: Modified run-length encoding. Only elements with duplicates are transferred as (N, E) terms
P12**: Decode a run-length encoded list
P13**: Run-length encoding of a list (direct solution)
P14*: Duplicate the elements of a list
P15**: Duplicate the elements of a list a given number of times
P16**: Drop every Nth element from a list
P17*: Split a list into two parts
P18**: Extract a slice from a list
P19**: Rotate a list N places to the left
P20*: Remove the Kth element from a list
P21*: Insert an element at a given position into a list
P22*: Create a list containing all integers within a given range
P23**: Extract a given number of randomly selected elements from a list
P24*: Lotto: Draw N different random numbers from the set 1..M
P25*: Generate a random permutation of the elements of a list
P26**: Generate the combinations of K distinct objects chosen from the N elements of a list
P27**: Group the elements of a set into disjoint subsets
P28**: Sorting a list of lists according to length of sublists