Exercises on the Crystal Track | Exercism

Hello World

The classical introductory exercise. Just say "Hello, World!"

Hamming

Calculate the Hamming difference between two DNA strands.

Gigasecond

Given a moment, determine the moment that would be after a gigasecond has passed.

RNA Transcription

Given a DNA strand, return its RNA Complement Transcription.

Bob

Bob is a lackadaisical teenager. In conversation, his responses are very limited.

Raindrops

Convert a number to a string, the contents of which depend on the number's factors.

Leap

Given a year, report if it is a leap year.

Triangle

Determine if a triangle is equilateral, isosceles, or scalene.

Difference Of Squares

Find the difference between the square of the sum and the sum of the squares of the first N natural numbers.

Pangram

Determine if a sentence is a pangram.

Largest Series Product

Given a string of digits, calculate the largest product for a contiguous substring of digits of length n.

Matching Brackets

Make sure the brackets and braces all match.

Sieve

Use the Sieve of Eratosthenes to find all the primes from 2 up to a given number.

Roman Numerals

Write a function to convert from normal numbers to Roman Numerals.

Atbash Cipher

Create an implementation of the atbash cipher, an ancient encryption system created in the Middle East.

Anagram

Given a word and a list of possible anagrams, select the correct sublist.

React

Implement a basic reactive system.

Acronym

Convert a long phrase to its acronym

Binary

Convert a binary number, represented as a string (e.g. '101010'), to its decimal equivalent using first principles

Binary Search Tree

Insert and search for numbers in a binary tree.

data structures

Run Length Encoding

Implement run-length encoding and decoding.

Pascal's Triangle

Compute Pascal's triangle up to a given number of rows.

Forth

Implement an evaluator for a very simple subset of Forth

Flatten Array

Take a nested list and return a single list with all values except nil/null

Armstrong Numbers

Determine if a number is an Armstrong number

Isogram

Determine if a word or phrase is an isogram.

Two Fer

Create a sentence of the form "One for X, one for me."

optional values

text formatting

Reverse String

Reverse a string

Collatz Conjecture

Calculate the number of steps to reach 1 using the Collatz conjecture

Scrabble Score

Given a word, compute the scrabble score for that word.

Space Age

Given an age in seconds, calculate how old someone is in terms of a given planet's solar years.

floating point numbers

ISBN Verifier

Check if a given string is a valid ISBN-10 number.

Grains

Calculate the number of grains of wheat on a chessboard given that the number on each square doubles.

Perfect Numbers

Determine if a number is perfect, abundant, or deficient based on Nicomachus' (60 - 120 CE) classification scheme for natural numbers.

Nth Prime

Given a number n, determine what the nth prime is.

Resistor Color

Convert a resistor band's color to its numeric representation

Strain

Implement the `keep` and `discard` operation on collections. Given a collection and a predicate on the collection's elements, `keep` returns a new collection containing those elements where the predicate is true, while `discard` returns a new collection containing those elements where the predicate is false.

All Your Base

Convert a number, represented as a sequence of digits in one base, to any other base.

Luhn

Given a number determine whether or not it is valid per the Luhn formula.

Secret Handshake

Given a decimal number, convert it to the appropriate sequence of events for a secret handshake.

bitwise operations

Sum Of Multiples

Given a number, find the sum of all the multiples of particular numbers up to but not including that number.

Darts

Write a function that returns the earned points in a single toss of a Darts game

Resistor Color Duo

Convert color codes, as used on resistors, to a numeric value.

Proverb

For want of a horseshoe nail, a kingdom was lost, or so the saying goes. Output the full text of this proverbial rhyme.