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Language tracks
Scala track
Exercises
Exercises on the Scala track
Join the Scala Track
91 exercises to help you master Scala
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
Leap
Given a year, report if it is a leap year.
integers
easy
Space Age
Given an age in seconds, calculate how old someone is in terms of a given planet's solar years.
dates
domain specific languages
enumerations
easy
Grade School
Given students' names along with the grade that they are in, create a roster for the school
maps
sequences
sorting
easy
Bob
Bob is a lackadaisical teenager. In conversation, his responses are very limited.
control flow if else statements
pattern matching
strings
easy
Hamming
Calculate the Hamming difference between two DNA strands.
filtering
optional values
strings
easy
ETL
We are going to do the `Transform` step of an Extract-Transform-Load.
lists
maps
sequences
strings
transforming
easy
Robot Simulator
Write a robot simulator.
enumerations
tuples
easy
Secret Handshake
Given a decimal number, convert it to the appropriate sequence of events for a secret handshake.
bitwise operations
lists
strings
easy
Sum Of Multiples
Given a number, find the sum of all the multiples of particular numbers up to but not including that number.
filtering
sets
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.
generics
lists
transforming
easy
Flatten Array
Take a nested list and return a single list with all values except nil/null
lists
pattern matching
recursion
easy
Collatz Conjecture
Calculate the number of steps to reach 1 using the Collatz conjecture
recursion
math
easy
Armstrong Numbers
Determine if a number is an Armstrong number
integers
math
easy
Perfect Numbers
Determine if a number is perfect, abundant, or deficient based on Nicomachus' (60 - 120 CE) classification scheme for natural numbers.
discriminated unions
enumerations
integers
math
medium
Matrix
Given a string representing a matrix of numbers, return the rows and columns of that matrix.
matrices
parsing
strings
vectors
easy
Gigasecond
Given a moment, determine the moment that would be after a gigasecond has passed.
dates
function overloading
time
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
Pangram
Determine if a sentence is a pangram.
strings
easy
Raindrops
Convert a number to a string, the content of which depends on the number's factors.
logic
strings
transforming
easy
Phone Number
Clean up user-entered phone numbers so that they can be sent SMS messages.
optional values
parsing
strings
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
generics
sequences
easy
Robot Name
Manage robot factory settings.
randomness
strings
easy
Grains
Calculate the number of grains of wheat on a chessboard given that the number on each square doubles.
optional values
easy
Scrabble Score
Given a word, compute the Scrabble score for that word.
strings
transforming
easy
RNA Transcription
Given a DNA strand, return its RNA Complement Transcription.
optional values
strings
transforming
easy
Triangle
Determine if a triangle is equilateral, isosceles, or scalene.
misc
easy
Binary Search
Implement a binary search algorithm.
arrays
optional values
searching
easy
Sieve
Use the Sieve of Eratosthenes to find all the primes from 2 up to a given number.
filtering
lists
math
easy
Isogram
Determine if a word or phrase is an isogram.
filtering
strings
easy
Clock
Implement a clock that handles times without dates.
structural equality
time
easy
Protein Translation
Translate RNA sequences into proteins.
sequences
strings
transforming
easy
Beer Song
Produce the lyrics to that beloved classic, that field-trip favorite: 99 Bottles of Beer on the Wall.
algorithms
control flow
strings
text formatting
medium
House
Output the nursery rhyme 'This is the House that Jack Built'.
algorithms
strings
text formatting
medium
Series
Given a string of digits, output all the contiguous substrings of length `n` in that string.
sequences
strings
transforming
medium
Word Count
Given a phrase, count the occurrences of each word in that phrase.
maps
strings
transforming
medium
Anagram
Given a word and a list of possible anagrams, select the correct sublist.
filtering
sequences
strings
medium
Nucleotide Count
Given a DNA string, compute how many times each nucleotide occurs in the string.
maps
strings
medium
Meetup
Calculate the date of meetups.
dates
medium
Prime Factors
Compute the prime factors of a given natural number.
algorithms
integers
lists
math
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.
enumerations
filtering
lists
medium
All Your Base
Convert a number, represented as a sequence of digits in one base, to any other base.
integers
lists
optional values
transforming
math
medium
Kindergarten Garden
Given a diagram, determine which plants each child in the kindergarten class is responsible for.
enumerations
lists
transforming
medium
Largest Series Product
Given a string of digits, calculate the largest product for a contiguous substring of digits of length n.
integers
optional values
strings
transforming
math
medium
Pascal's Triangle
Compute Pascal's triangle up to a given number of rows.
control flow loops
lists
math
medium
Pythagorean Triplet
There exists exactly one Pythagorean triplet for which a + b + c = 1000. Find the product a * b * c.
integers
sequences
tuples
math
medium
Saddle Points
Detect saddle points in a matrix.
lists
matrices
sets
tuples
medium
Acronym
Convert a long phrase to its acronym
strings
transforming
medium
Run Length Encoding
Implement run-length encoding and decoding.
algorithms
strings
transforming
medium
Roman Numerals
Write a function to convert from normal numbers to Roman Numerals.
algorithms
sequences
transforming
medium
Simple Linked List
Write a simple linked list implementation that uses Elements and a List
classes
generics
lists
transforming
medium
Atbash Cipher
Create an implementation of the atbash cipher, an ancient encryption system created in the Middle East.
security
strings
transforming
medium
Simple Cipher
Implement a simple shift cipher like Caesar and a more secure substitution cipher
algorithms
optional values
strings
transforming
medium
Bank Account
Simulate a bank account supporting opening/closing, withdraws, and deposits of money. Watch out for concurrent transactions!
parallellism
medium
Crypto Square
Implement the classic method for composing secret messages called a square code.
lists
security
strings
transforming
medium
Matching Brackets
Make sure the brackets and braces all match.
parsing
strings
medium
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.
games
logic
optional values
strings
medium
Luhn
Given a number determine whether or not it is valid per the Luhn formula.
algorithms
strings
transforming
medium
Food Chain
Generate the lyrics of the song 'I Know an Old Lady Who Swallowed a Fly'
algorithms
text formatting
medium
Linked List
Implement a doubly linked list
generics
lists
optional values
medium
Spiral Matrix
Given the size, return a square matrix of numbers in spiral order.
matrices
medium
Custom Set
Create a custom set type.
generics
lists
sets
medium
Parallel Letter Frequency
Count the frequency of letters in texts using parallel computation.
dictionaries
maps
parallellism
sequences
strings
transforming
medium
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.
recursion
medium
Nth Prime
Given a number n, determine what the nth prime is.
algorithms
optional values
math
medium
Palindrome Products
Detect palindrome products in a given range.
algorithms
optional values
sets
strings
tuples
math
medium
OCR Numbers
Given a 3 x 4 grid of pipes, underscores, and spaces, determine which number is represented, or whether it is garbled.
lists
parsing
pattern recognition
strings
transforming
medium
Pig Latin
Implement a program that translates from English to Pig Latin
strings
transforming
medium
Binary Search Tree
Insert and search for numbers in a binary tree.
generics
lists
searching
trees
medium
Rail Fence Cipher
Implement encoding and decoding for the rail fence cipher.
algorithms
strings
transforming
medium
Bowling
Score a bowling game
algorithms
control flow if else statements
lists
medium
Dominoes
Make a chain of dominoes.
games
lists
optional values
tuples
medium
Sublist
Write a function to determine if a list is a sublist of another list.
enumerations
generics
lists
medium
Minesweeper
Add the numbers to a minesweeper board
lists
parsing
strings
transforming
medium
Wordy
Parse and evaluate simple math word problems returning the answer as an integer.
optional values
parsing
strings
transforming
medium
Change
Correctly determine change to be given using the least number of coins
integers
lists
optional values
hard
Connect
Compute the result for a game of Hex / Polygon
algorithms
games
graphs
optional values
recursion
searching
hard
Zebra Puzzle
Solve the zebra puzzle.
logic
hard
Say
Given a number from 0 to 999,999,999,999, spell out that number in English.
optional values
strings
text formatting
transforming
hard
Alphametics
Write a function to solve alphametics puzzles.
maps
optional values
parsing
strings
hard
SGF Parsing
Parsing a Smart Game Format string.
parsing
transforming
hard
Lens Person
Use lenses to update nested records (specific to languages with immutable data).
misc
hard
Variable Length Quantity
Implement variable length quantity encoding and decoding.
algorithms
bitwise operations
discriminated unions
lists
hard
Zipper
Creating a zipper for a binary tree.
generics
optional values
trees
hard
Forth
Implement an evaluator for a very simple subset of Forth
parsing
strings
medium
Diamond
Given a letter, print a diamond starting with 'A' with the supplied letter at the widest point.
lists
strings
text formatting
medium
Complex Numbers
Implement complex numbers.
math
medium
Rotational Cipher
Create an implementation of the rotational cipher, also sometimes called the Caesar cipher.
math
security
strings
transforming
easy
High Scores
Manage a player's High Score list
lists
strings
easy
Darts
Write a function that returns the earned points in a single toss of a Darts game
math
control flow if else statements
floating point numbers