Exercises on the Java Track | Exercism

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Hello World

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

Two Fer

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

Reverse String

Reverse a string

Leap

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

Resistor Color

Convert a resistor band's color to its numeric representation

Resistor Color Duo

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

Darts

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

Armstrong Numbers

Determine if a number is an Armstrong number

RNA Transcription

Given a DNA strand, return its RNA Complement Transcription.

D&D Character

Randomly generate Dungeons & Dragons characters

Grains

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

Pangram

Determine if a sentence is a pangram.

pattern matching

regular expressions

Hamming

Calculate the Hamming difference between two DNA strands.

Gigasecond

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

Space Age

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

floating point numbers

Acronym

Convert a long phrase to its acronym

Scrabble Score

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

pattern matching

Raindrops

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

Difference Of Squares

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

Secret Handshake

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

bitwise operations

Perfect Numbers

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

exception handling

Protein Translation

Translate RNA sequences into proteins.

Say

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

Micro Blog

Given an input string, truncate it to 5 characters.

Yacht

Score a single throw of dice in the game Yacht

pattern matching

Proverb

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

ISBN Verifier

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

Sum Of Multiples

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

Luhn

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

type conversion

Matrix

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

pattern matching

type conversion

Triangle

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

exception handling

Largest Series Product

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

type conversion

Sieve

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

Twelve Days

Output the lyrics to 'The Twelve Days of Christmas'

Rotational Cipher

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

Kindergarten Garden

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

pattern recognition

Collatz Conjecture

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

exception handling

Nth Prime

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

exception handling

Saddle Points

Detect saddle points in a matrix.

Error Handling

Implement various kinds of error handling and resource management

exception handling

optional values

Diamond

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

text formatting

Isogram

Determine if a word or phrase is an isogram.

Variable Length Quantity

Implement variable length quantity encoding and decoding.

bitwise operations

exception handling

Flatten Array

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

Pig Latin

Implement a program that translates from English to Pig Latin

Phone Number

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

pattern matching

regular expressions

Nucleotide Count

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

exception handling

Word Count

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

Run Length Encoding

Implement run-length encoding and decoding.

pattern matching

Robot Name

Manage robot factory settings.

pattern matching

regular expressions

text formatting

Prime Factors

Compute the prime factors of a given natural number.

Allergies

Given a person's allergy score, determine whether or not they're allergic to a given item, and their full list of allergies.

Bob

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

Pascal's Triangle

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

exception handling

Matching Brackets

Make sure the brackets and braces all match.

Series

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

type conversion

Atbash Cipher

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

Grep

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

pattern matching

Knapsack

Given a knapsack that can only carry a certain weight, determine which items to put in the knapsack in order to maximize their combined value.

Alphametics

Write a function to solve alphametics puzzles.

Spiral Matrix

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

Rest API

Implement a RESTful API for tracking IOUs.

Roman Numerals

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

Transpose

Take input text and output it transposed.

text formatting

House

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

text formatting

Food Chain

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

Beer Song

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

text formatting

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.

ETL

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

Grade School

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

Robot Simulator

Write a robot simulator.

Binary Search

Implement a binary search algorithm.

Minesweeper

Add the numbers to a minesweeper board

Wordy

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

exception handling

pattern matching

regular expressions

All Your Base

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

exception handling

Bank Account

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

exception handling

Bowling

Score a bowling game

exception handling

Linked List

Implement a doubly linked list

Tournament

Tally the results of a small football competition.

text formatting

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.

Affine Cipher

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

text formatting

Two Bucket

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

Zebra Puzzle

Solve the zebra puzzle.

Anagram

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

Sublist

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

Word Search

Create a program to solve a word search puzzle.

pattern matching

Simple Linked List

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

exception handling

Binary Search Tree

Insert and search for numbers in a binary tree.

Meetup

Calculate the date of meetups.

Crypto Square

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

text formatting

Markdown

Refactor a Markdown parser

pattern matching

Poker

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

Clock

Implement a clock that handles times without dates.

object oriented programming

Tree Building

Refactor a tree building algorithm.

Zipper

Creating a zipper for a binary tree.

Go Counting

Count the scored points on a Go board.

Dominoes

Make a chain of dominoes.

exception handling

OCR Numbers

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

exception handling

Circular Buffer

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

exception handling

Rectangles

Count the rectangles in an ASCII diagram.

pattern recognition

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

Diffie Hellman

Diffie-Hellman key exchange.

Simple Cipher

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

exception handling

Complex Numbers

Implement complex numbers.

floating point numbers

Rational Numbers

Implement rational numbers.

floating point numbers

List Ops

Implement basic list operations

functional programming

Change

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

exception handling

Palindrome Products

Detect palindrome products in a given range.

Hangman

Implement the logic of the hangman game using functional reactive programming.

reactive programming

functional programming

Pythagorean Triplet

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

Forth

Implement an evaluator for a very simple subset of Forth

exception handling

Custom Set

Create a custom set type.

Satellite

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