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Language tracks
Elm track
Exercises
Exercises on the Elm track
Join the Elm Track
46 exercises to help you master Elm
easy
Hello World
The classical introductory exercise. Just say "Hello, World!"
strings
easy
Two Fer
Create a sentence of the form "One for X, one for me."
strings
easy
Bob
Bob is a lackadaisical teenager. In conversation, his responses are very limited.
conditionals
strings
text formatting
easy
Difference Of Squares
Find the difference between the square of the sum and the sum of the squares of the first N natural numbers.
integers
math
easy
Gigasecond
Given a moment, determine the moment that would be after a gigasecond has passed.
dates
easy
Leap
Given a year, report if it is a leap year.
conditionals
integers
easy
RNA Transcription
Given a DNA strand, return its RNA Complement Transcription.
strings
transforming
easy
Space Age
Given an age in seconds, calculate how old someone is in terms of a given planet's solar years.
floating point numbers
easy
Sum Of Multiples
Given a number, find the sum of all the multiples of particular numbers up to but not including that number.
lists
transforming
math
easy
Accumulate
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.
recursion
transforming
easy
Collatz Conjecture
Calculate the number of steps to reach 1 using the Collatz conjecture
math
easy
ETL
We are going to do the `Transform` step of an Extract-Transform-Load.
maps
transforming
easy
Grade School
Given students' names along with the grade that they are in, create a roster for the school
maps
sorting
easy
Grains
Calculate the number of grains of wheat on a chessboard given that the number on each square doubles.
integers
easy
Hamming
Calculate the Hamming difference between two DNA strands.
filtering
strings
easy
Nucleotide Count
Given a DNA string, compute how many times each nucleotide occurs in the string.
maps
strings
easy
Pangram
Determine if a sentence is a pangram.
booleans
strings
easy
Raindrops
Convert a number to a string, the content of which depends on the number's factors.
filtering
text formatting
easy
Armstrong Numbers
Determine if a number is an Armstrong number
strings
integers
lists
algorithms
math
easy
Binary Search
Implement a binary search algorithm.
algorithms
recursion
lists
easy
Isogram
Determine if a word or phrase is an isogram.
filtering
strings
easy
Phone Number
Clean up user-entered phone numbers so that they can be sent SMS messages.
parsing
transforming
easy
Robot Simulator
Write a robot simulator.
records
tuples
easy
Scrabble Score
Given a word, compute the Scrabble score for that word.
transforming
easy
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.
filtering
sequences
easy
Triangle
Determine if a triangle is equilateral, isosceles, or scalene.
misc
medium
Acronym
Convert a long phrase to its acronym
strings
transforming
medium
All Your Base
Convert a number, represented as a sequence of digits in one base, to any other base.
integers
math
transforming
medium
Allergies
Given a person's allergy score, determine whether or not they're allergic to a given item, and their full list of allergies.
bitwise operations
enumerations
filtering
medium
Anagram
Given a word and a list of possible anagrams, select the correct sublist.
filtering
strings
medium
Largest Series Product
Given a string of digits, calculate the largest product for a contiguous substring of digits of length n.
integers
math
strings
transforming
medium
List Ops
Implement basic list operations
lists
recursion
medium
Pascal's Triangle
Compute Pascal's triangle up to a given number of rows.
lists
math
recursion
medium
Series
Given a string of digits, output all the contiguous substrings of length `n` in that string.
lists
strings
transforming
medium
Twelve Days
Output the lyrics to 'The Twelve Days of Christmas'
conditionals
strings
text formatting
medium
Word Count
Given a phrase, count the occurrences of each word in that phrase.
maps
strings
transforming
medium
Atbash Cipher
Create an implementation of the atbash cipher, an ancient encryption system created in the Middle East.
algorithms
strings
transforming
medium
Luhn
Given a number determine whether or not it is valid per the Luhn formula.
algorithms
strings
transforming
medium
Pythagorean Triplet
There exists exactly one Pythagorean triplet for which a + b + c = 1000. Find the product a * b * c.
algorithms
conditionals
loops
integers
math
medium
Roman Numerals
Write a function to convert from normal numbers to Roman Numerals.
recursion
transforming
medium
Run Length Encoding
Implement run-length encoding and decoding.
algorithms
transforming
medium
Transpose
Take input text and output it transposed.
matrices
medium
Matching Brackets
Make sure the brackets and braces all match.
parsing
stacks
medium
Sublist
Write a function to determine if a list is a sublist of another list.
lists
recursion
hard
Say
Given a number from 0 to 999,999,999,999, spell out that number in English.
strings
text formatting
transforming
hard
Wordy
Parse and evaluate simple math word problems returning the answer as an integer.
parsing