Exercises on the Erlang Track | Exercism

Hello World

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

Two Fer

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

Leap

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

control flow conditionals

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.

Collatz Conjecture

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

control flow conditionals

pattern matching

Raindrops

Convert a number to a string, the content of which depends on the number's factors.

control flow conditionals

pattern matching

RNA Transcription

Given a DNA strand, return its RNA Complement Transcription.

control flow conditionals

pattern matching

Bob

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

pattern matching

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.

control flow conditionals

Hamming

Calculate the Hamming difference between two DNA strands.

Space Age

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

Darts

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

control flow conditionals

Secret Handshake

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

control flow conditionals

pattern matching

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.

control flow conditionals

Diamond

Given a letter, print a diamond starting with 'A' with the supplied letter at the widest point.

Grains

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

bitwise operations

pattern matching

Isogram

Determine if a word or phrase is an isogram.

control flow conditionals

pattern matching

Pangram

Determine if a sentence is a pangram.

control flow conditionals

control flow recursion

Nucleotide Count

Given a DNA string, compute how many times each nucleotide occurs in the string.

Difference Of Squares

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

control flow recursion

pattern matching

Triangle

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

control flow conditionals

Prime Factors

Compute the prime factors of a given natural number.

Sum Of Multiples

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

Perfect Numbers

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

Armstrong Numbers

Determine if a number is an Armstrong number

Anagram

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

Atbash Cipher

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

Phone Number

Clean up user-entered phone numbers so that they can be sent SMS messages.

ISBN Verifier

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

Bracket Push

Gigasecond

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

Scrabble Score

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

pattern matching

Run Length Encoding

Implement run-length encoding and decoding.

Protein Translation

Translate RNA sequences into proteins.

control flow conditionals

pattern matching

Robot Simulator

Write a robot simulator.

control flow conditionals

control flow recursion

Grade School

Given students' names along with the grade that they are in, create a roster for the school

pattern matching

Sublist

Write a function to determine if a list is a sublist of another list.

Word Count

Given a phrase, count the occurrences of each word in that phrase.

Clock

Implement a clock that handles times without dates.

control flow conditionals

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

Transpose

Take input text and output it transposed.

All Your Base

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

Series

Given a string of digits, output all the contiguous substrings of length `n` in that string.

Parallel Letter Frequency

Count the frequency of letters in texts using parallel computation.

pattern matching

Roman Numerals

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

pattern matching

Sieve

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

Saddle Points

Detect saddle points in a matrix.

Nth Prime

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

Largest Series Product

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

Rational Numbers

Implement rational numbers.

Complex Numbers

Implement complex numbers.

Rotational Cipher

Create an implementation of the rotational cipher, also sometimes called the Caesar cipher.

Change

Correctly determine change to be given using the least number of coins

Variable Length Quantity

Implement variable length quantity encoding and decoding.

bitwise operations

Satellite

Rebuild binary trees from pre-order and in-order traversals.

ETL

We are going to do the `Transform` step of an Extract-Transform-Load.

Bank Account

Simulate a bank account supporting opening/closing, withdraws, and deposits of money. Watch out for concurrent transactions!

pattern matching

Luhn

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

Pythagorean Triplet

There exists exactly one Pythagorean triplet for which a + b + c = 1000. Find the product a * b * c.

Custom Set

Create a custom set type.

Meetup

Calculate the date of meetups.

control flow conditionals

Crypto Square

Implement the classic method for composing secret messages called a square code.

Rail Fence Cipher

Implement encoding and decoding for the rail fence cipher.

Pascal's Triangle

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

pattern matching

Palindrome Products

Detect palindrome products in a given range.

Poker

Pick the best hand(s) from a list of poker hands.

Forth

Implement an evaluator for a very simple subset of Forth

Circular Buffer

A data structure that uses a single, fixed-size buffer as if it were connected end-to-end.

Minesweeper

Add the numbers to a minesweeper board

Beer Song

Produce the lyrics to that beloved classic, that field-trip favorite: 99 Bottles of Beer on the Wall.

text formatting

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.

Dominoes

Make a chain of dominoes.

Zipper

Creating a zipper for a binary tree.

control flow recursion

Spiral Matrix

Given the size, return a square matrix of numbers in spiral order.

Connect

Compute the result for a game of Hex / Polygon

List Ops

Implement basic list operations

Simple Linked List

Write a simple linked list implementation that uses Elements and a List

data structures