Add new Factor exercises
One of the easiest ways to add new exercises to the Factor track is to translate them from other language tracks on Exercism. This page lists all of the problem specifications in the common pool of exercises which have not yet been implemented in Factor.
The icon links to the language-independent description of the problem.
The icon links to the canonical test data.
We also link to all the implementations of each exercise in other languages, which you can use for inspiration.
Once you've picked an exercise, follow the instructions in this guide and submit your pull request to the Factor track repository on GitHub.
Calculate the Hamming difference between two DNA strands.
Given a DNA strand, return its RNA complement (per RNA transcription).
Bob is a lackadaisical teenager. In conversation, his responses are very limited.
Difference Of Squares
Find the difference between the square of the sum and the sum of the squares of the first N natural numbers.
Given a word and a list of possible anagrams, select the correct sublist.
Convert a number to a string, the contents of which depend on the number's factors.
Given a phrase, count the occurrences of each word in that phrase.
Determine if a triangle is equilateral, isosceles, or scalene.
Create an implementation of the atbash cipher, an ancient encryption system created in the Middle East.
Clean up user-entered phone numbers so that they can be sent SMS messages.
Write a function to convert from normal numbers to Roman Numerals.
Given a DNA string, compute how many times each nucleotide occurs in the string.
Determine if a sentence is a pangram.
Calculate the moment when someone has lived for 10^9 seconds.
Calculate the number of grains of wheat on a chessboard given that the number on each square doubles.
Given a word, compute the scrabble score for that word.
Given a person's allergy score, determine whether or not they're allergic to a given item, and their full list of allergies.
We are going to do the `Transform` step of an Extract-Transform-Load.
Produce the lyrics to that beloved classic, that field-trip favorite: 99 Bottles of Beer on the Wall.
Given an age in seconds, calculate how old someone is in terms of a given planet's solar years.
Largest Series Product
Given a string of digits, calculate the largest product for a contiguous substring of digits of length n.
Sum Of Multiples
Given a number, find the sum of all the multiples of particular numbers up to but not including that number.
Compute Pascal's triangle up to a given number of rows.
Manage robot factory settings.
Convert a long phrase to its acronym
Implement a clock that handles times without dates.
Calculate the number of steps to reach 1 using the Collatz conjecture
Given students' names along with the grade that they are in, create a roster for the school
Given a number determine whether or not it is valid per the Luhn formula.
Calculate the date of meetups.
Given a number n, determine what the nth prime is.
Use the Sieve of Eratosthenes to find all the primes from 2 up to a given number.
All Your Base
Convert a number, represented as a sequence of digits in one base, to any other base.
Determine if a number is perfect, abundant, or deficient based on Nicomachus' (60 - 120 CE) classification scheme for natural numbers.
Given a string of digits, output all the contiguous substrings of length `n` in that string.
Implement a binary search algorithm.
Compute the prime factors of a given natural number.
Make sure the brackets and braces all match.
Implement the classic method for composing secret messages called a square code.
Implement the `accumulate` operation, which, given a collection and an operation to perform on each element of the collection, returns a new collection containing the result of applying that operation to each element of the input collection.
Implement a program that translates from English to Pig Latin
Given the position of two queens on a chess board, indicate whether or not they are positioned so that they can attack each other.
Run Length Encoding
Implement run-length encoding and decoding.
Given a number from 0 to 999,999,999,999, spell out that number in English.
Add the numbers to a minesweeper board
Given a decimal number, convert it to the appropriate sequence of events for a secret handshake.
Write a function to determine if a list is a sublist of another list.
Parse and evaluate simple math word problems returning the answer as an integer.
Take a nested list and return a single list with all values except nil/null
Binary Search Tree
Insert and search for numbers in a binary tree.
Given a letter, print a diamond starting with 'A' with the supplied letter at the widest point.
Create a custom set type.
Implement a doubly linked list
Implement basic list operations
Given a 3 x 4 grid of pipes, underscores, and spaces, determine which number is represented, or whether it is garbled.
Create an implementation of the rotational cipher, also sometimes called the Caesar cipher.
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.
Correctly determine change to be given using the least number of coins
Detect palindrome products in a given range.
There exists exactly one Pythagorean triplet for which a + b + c = 1000. Find the product a * b * c.
Detect saddle points in a matrix.
A data structure that uses a single, fixed-size buffer as if it were connected end-to-end.
Generate the lyrics of the song 'I Know an Old Lady Who Swallowed a Fly'
Given a diagram, determine which plants each child in the kindergarten class is responsible for.
Given a string representing a matrix of numbers, return the rows and columns of that matrix.
Translate RNA sequences into proteins.
Implement a basic reactive system.
Implement a simple shift cipher like Caesar and a more secure substitution cipher
Take input text and output it transposed.
Simulate a bank account supporting opening/closing, withdraws, and deposits of money. Watch out for concurrent transactions!
Simple Linked List
Write a simple linked list implementation that uses Elements and a List
Compute the result for a game of Hex / Polygon
Implement an evaluator for a very simple subset of Forth
Output the nursery rhyme 'This is the House that Jack Built'.
Check if a given string is a valid ISBN-10 number.
Given the size, return a square matrix of numbers in spiral order.
Tally the results of a small football competition.
Output the lyrics to 'The Twelve Days of Christmas'
Write a function to solve alphametics puzzles.
Implement complex numbers.
Make a chain of dominoes.
Pick the best hand(s) from a list of poker hands.
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.
Parallel Letter Frequency
Count the frequency of letters in texts using parallel computation.
Rail Fence Cipher
Implement encoding and decoding for the rail fence cipher.
Creating a zipper for a binary tree.
Diffie-Hellman key exchange.
Count the rectangles in an ASCII diagram.
Given two buckets of different size, demonstrate how to measure an exact number of liters.
Variable Length Quantity
Implement variable length quantity encoding and decoding.
Refactor a Markdown parser
Reparent a graph on a selected node
For want of a horseshoe nail, a kingdom was lost, or so the saying goes. Output the full text of this proverbial rhyme.
Create a program to solve a word search puzzle.
Implement various kinds of error handling and resource management
Search a file for lines matching a regular expression pattern. Return the line number and contents of each matching line.
Generate musical scales, given a starting note and a set of intervals.
Determine if a number is an Armstrong number
Write a Domain Specific Language similar to the Graphviz dot language
Count the scored points on a Go board.
Parsing a Smart Game Format string.
Refactor a tree building algorithm.
Implement the logic of the hangman game using functional reactive programming.
Refactor a ledger printer.
Use lenses to update nested records (specific to languages with immutable data).
Report network IO statistics