When you're logged in, you can say exercism fetch java to get the next available exercise on the track.

Every time you submit a solution to an exercise, you will get the next in line the next time you fetch.

If you want to try a specific exercise, you can always fetch it directly (commands are listed below).

The exercises are ordered roughly in order of difficulty.

Available Exercises

  • Hello World The classical introductory exercise. Just say "Hello, World!"
  • Two Fer Create a sentence of the form "One for X, one for me."
  • Rna Transcription Given a DNA strand, return its RNA complement (per RNA transcription).
  • Pangram Determine if a sentence is a pangram.
  • Hamming Calculate the Hamming difference between two DNA strands.
  • Gigasecond Calculate the moment when someone has lived for 10^9 seconds.
  • Space Age Given an age in seconds, calculate how old someone is in terms of a given planet's solar years.
  • Acronym Convert a long phrase to its acronym
  • Scrabble Score Given a word, compute the scrabble score for that word.
  • Raindrops Convert a number to a string, the contents of which depend on the number's factors.
  • Difference Of Squares Find the difference between the square of the sum and the sum of the squares of the first N natural numbers.
  • Secret Handshake Given a decimal number, convert it to the appropriate sequence of events for a secret handshake.
  • Perfect Numbers Determine if a number is perfect, abundant, or deficient based on Nicomachus' (60 - 120 CE) classification scheme for natural numbers.
  • Protein Translation Translate RNA sequences into proteins.
  • Isbn Verifier Check if a given string is a valid ISBN-10 number.
  • Sum Of Multiples Given a number, find the sum of all the multiples of particular numbers up to but not including that number.
  • Luhn Given a number determine whether or not it is valid per the Luhn formula.
  • Matrix Given a string representing a matrix of numbers, return the rows and columns of that matrix.
  • Triangle Determine if a triangle is equilateral, isosceles, or scalene.
  • Largest Series Product Given a string of digits, calculate the largest product for a contiguous substring of digits of length n.
  • Sieve Use the Sieve of Eratosthenes to find all the primes from 2 up to a given number.
  • Twelve Days Output the lyrics to 'The Twelve Days of Christmas'
  • Rotational Cipher Create an implementation of the rotational cipher, also sometimes called the Caesar cipher.
  • Kindergarten Garden Given a diagram, determine which plants each child in the kindergarten class is responsible for.
  • Collatz Conjecture Calculate the number of steps to reach 1 using the Collatz conjecture
  • Nth Prime Given a number n, determine what the nth prime is.
  • Saddle Points Detect saddle points in a matrix.
  • Diamond Given a letter, print a diamond starting with 'A' with the supplied letter at the widest point.
  • Isogram Determine if a word or phrase is an isogram.
  • Flatten Array Take a nested list and return a single list with all values except nil/null
  • Pig Latin Implement a program that translates from English to Pig Latin
  • Phone Number Clean up user-entered phone numbers so that they can be sent SMS messages.
  • Nucleotide Count Given a DNA string, compute how many times each nucleotide occurs in the string.
  • Word Count Given a phrase, count the occurrences of each word in that phrase.
  • Run Length Encoding Implement run-length encoding and decoding.
  • Robot Name Manage robot factory settings.
  • Prime Factors Compute the prime factors of a given natural number.
  • Allergies Given a person's allergy score, determine whether or not they're allergic to a given item, and their full list of allergies.
  • Bob Bob is a lackadaisical teenager. In conversation, his responses are very limited.
  • Pascals Triangle Compute Pascal's triangle up to a given number of rows.
  • Bracket Push Make sure the brackets and braces all match.
  • Series Given a string of digits, output all the contiguous substrings of length `n` in that string.
  • Atbash Cipher Create an implementation of the atbash cipher, an ancient encryption system created in the Middle East.
  • Spiral Matrix Given the size, return a square matrix of numbers in spiral order.
  • Roman Numerals Write a function to convert from normal numbers to Roman Numerals.
  • Transpose Take input text and output it transposed.
  • House Output the nursery rhyme 'This is the House that Jack Built'.
  • Food Chain Generate the lyrics of the song 'I Know an Old Lady Who Swallowed a Fly'
  • Beer Song Produce the lyrics to that beloved classic, that field-trip favorite: 99 Bottles of Beer on the Wall.
  • Queen Attack Given the position of two queens on a chess board, indicate whether or not they are positioned so that they can attack each other.
  • Etl We are going to do the `Transform` step of an Extract-Transform-Load.
  • Grade School Given students' names along with the grade that they are in, create a roster for the school
  • Robot Simulator Write a robot simulator.
  • Binary Search Implement a binary search algorithm.
  • Minesweeper Add the numbers to a minesweeper board
  • Wordy Parse and evaluate simple math word problems returning the answer as an integer.
  • All Your Base Convert a number, represented as a sequence of digits in one base, to any other base.
  • Bank Account Simulate a bank account supporting opening/closing, withdraws, and deposits of money. Watch out for concurrent transactions!
  • Bowling Score a bowling game
  • Linked List Implement a doubly linked list
  • Tournament Tally the results of a small football competition.
  • Anagram Given a word and a list of possible anagrams, select the correct sublist.
  • Sublist Write a function to determine if a list is a sublist of another list.
  • Word Search Create a program to solve a word search puzzle.
  • Simple Linked List Write a simple linked list implementation that uses Elements and a List
  • Binary Search Tree Insert and search for numbers in a binary tree.
  • Meetup Calculate the date of meetups.
  • Crypto Square Implement the classic method for composing secret messages called a square code.
  • Poker Pick the best hand(s) from a list of poker hands.
  • Clock Implement a clock that handles times without dates.
  • Ocr Numbers Given a 3 x 4 grid of pipes, underscores, and spaces, determine which number is represented, or whether it is garbled.
  • Circular Buffer A data structure that uses a single, fixed-size buffer as if it were connected end-to-end.
  • Rectangles Count the rectangles in an ASCII diagram.
  • Book Store To try and encourage more sales of different books from a popular 5 book series, a bookshop has decided to offer discounts of multiple-book purchases.
  • Simple Cipher Implement a simple shift cipher like Caesar and a more secure substitution cipher
  • Complex Numbers Implement complex numbers.
  • List Ops Implement basic list operations
  • Change Correctly determine change to be given using the least number of coins
  • Palindrome Products Detect palindrome products in a given range.
  • Pythagorean Triplet There exists exactly one Pythagorean triplet for which a + b + c = 1000. Find the product a * b * c.
  • Forth Implement an evaluator for a very simple subset of Forth
  • Custom Set Create a custom set type.