Exercises on the Ruby 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."

Resistor Color Duo

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

Acronym

Convert a long phrase to its acronym

regular expressions

High Scores

Manage a player's High Score list

Matrix

Given a string representing a matrix of numbers, return the rows and columns of that matrix.

exception handling

type conversion

Series

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

Word Count

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

Hamming

Calculate the Hamming difference between two DNA strands.

Raindrops

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

Isogram

Determine if a word or phrase is an isogram.

regular expressions

Scrabble Score

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

Luhn

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

Clock

Implement a clock that handles times without dates.

text formatting

Twelve Days

Output the lyrics to 'The Twelve Days of Christmas'

pattern recognition

text formatting

Tournament

Tally the results of a small football competition.

text formatting

Armstrong Numbers

Determine if a number is an Armstrong number

Difference Of Squares

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

Gigasecond

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

Grains

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

bitwise operations

RNA Transcription

Given a DNA strand, return its RNA Complement Transcription.

Robot Name

Manage robot factory settings.

Pangram

Determine if a sentence is a pangram.

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.

Nth Prime

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

Leap

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

Bob

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

Run Length Encoding

Implement run-length encoding and decoding.

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.

Sum Of Multiples

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

Grade School

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

Phone Number

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

regular expressions

text formatting

Prime Factors

Compute the prime factors of a given natural number.

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.

ETL

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

Beer Song

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

text formatting

Bowling

Score a bowling game

Space Age

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

floating point numbers

if else statements

Anagram

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

Binary Search Tree

Insert and search for numbers in a binary tree.

Crypto Square

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

text formatting

Alphametics

Write a function to solve alphametics puzzles.

Rail Fence Cipher

Implement encoding and decoding for the rail fence cipher.

text formatting

Nucleotide Count

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

Flatten Array

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

Say

Given a number from 0 to 999,999,999,999, spell out that number in English.

text formatting

Meetup

Calculate the date of meetups.

type conversion

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.

Palindrome Products

Detect palindrome products in a given range.

Matching Brackets

Make sure the brackets and braces all match.

Food Chain

Generate the lyrics of the song 'I Know an Old Lady Who Swallowed a Fly'

text formatting

Saddle Points

Detect saddle points in a matrix.

Triangle

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

Atbash Cipher

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

House

Output the nursery rhyme 'This is the House that Jack Built'.

text formatting

Secret Handshake

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

bitwise operations

Proverb

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

OCR Numbers

Given a 3 x 4 grid of pipes, underscores, and spaces, determine which number is represented, or whether it is garbled.

pattern recognition

Pig Latin

Implement a program that translates from English to Pig Latin

Simple Linked List

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

Simple Cipher

Implement a simple shift cipher like Caesar and a more secure substitution cipher

Wordy

Parse and evaluate simple math word problems returning the answer as an integer.

type conversion

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

Poker

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

pattern matching

Kindergarten Garden

Given a diagram, determine which plants each child in the kindergarten class is responsible for.

Largest Series Product

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

Pythagorean Triplet

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

Scale Generator

Generate musical scales, given a starting note and a set of intervals.

pattern matching

Protein Translation

Translate RNA sequences into proteins.

Perfect Numbers

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

Circular Buffer

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

Diamond

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

text formatting

Custom Set

Create a custom set type.

Transpose

Take input text and output it transposed.

Pascal's Triangle

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

Linked List

Implement a doubly linked list

Binary Search

Implement a binary search algorithm.

Minesweeper

Add the numbers to a minesweeper board

Robot Simulator

Write a robot simulator.

All Your Base

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

Connect

Compute the result for a game of Hex / Polygon

Change

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

Collatz Conjecture

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

control flow loops

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.

floating point numbers

Rotational Cipher

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

ISBN Verifier

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

Dominoes

Make a chain of dominoes.

Two Bucket

Given two buckets of different size, demonstrate how to measure an exact number of liters.

List Ops

Implement basic list operations

functional programming

type conversion

Affine Cipher

Create an implementation of the Affine cipher, an ancient encryption algorithm from the Middle East.

Complex Numbers

Implement complex numbers.

Zipper

Creating a zipper for a binary tree.

data structures

Grep

Search a file for lines matching a regular expression pattern. Return the line number and contents of each matching line.

pattern matching

regular expressions

text formatting

Resistor Color

Convert a resistor band's color to its numeric representation

Resistor Color Trio

Convert color codes, as used on resistors, to a human-readable label.

Darts

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