Sign up
Log in
Home
Language tracks
C# track
Exercises
Exercises on the C# track
Join the C# Track
120 exercises to help you master C#
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."
optional values
strings
easy
Leap
Given a year, report if it is a leap year.
integers
conditionals
easy
Gigasecond
Given a moment, determine the moment that would be after a gigasecond has passed.
dates
easy
Resistor Color
Convert a resistor band's color to its numeric representation
arrays
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
High Scores
Manage a player's High Score list
lists
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.
dictionaries
strings
easy
Robot Name
Manage robot factory settings.
classes
randomness
strings
easy
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
filtering
easy
Grade School
Given students' names along with the grade that they are in, create a roster for the school
lists
sorting
medium
Rotational Cipher
Create an implementation of the rotational cipher, also sometimes called the Caesar cipher.
algorithms
strings
transforming
medium
Circular Buffer
A data structure that uses a single, fixed-size buffer as if it were connected end-to-end.
classes
queues
medium
Clock
Implement a clock that handles times without dates.
classes
equality
medium
Bob
Bob is a lackadaisical teenager. In conversation, his responses are very limited.
strings
conditionals
medium
Matching Brackets
Make sure the brackets and braces all match.
parsing
strings
medium
Spiral Matrix
Given the size, return a square matrix of numbers in spiral order.
algorithms
matrices
medium
Tournament
Tally the results of a small football competition.
parsing
strings
medium
Variable Length Quantity
Implement variable length quantity encoding and decoding.
algorithms
bitwise operations
hard
Dominoes
Make a chain of dominoes.
arrays
tuples
hard
Forth
Implement an evaluator for a very simple subset of Forth
parsing
stacks
easy
Reverse String
Reverse a string
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.
arrays
transforming
math
easy
Series
Given a string of digits, output all the contiguous substrings of length `n` in that string.
arrays
strings
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.
extension methods
sequences
transforming
easy
Collatz Conjecture
Calculate the number of steps to reach 1 using the Collatz conjecture
algorithms
integers
math
conditionals
loops
easy
Armstrong Numbers
Determine if a number is an Armstrong number
math
medium
Rational Numbers
Implement rational numbers.
math
easy
RNA Transcription
Given a DNA strand, return its RNA Complement Transcription.
strings
transforming
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
loops
easy
Grains
Calculate the number of grains of wheat on a chessboard given that the number on each square doubles.
integers
easy
Pangram
Determine if a sentence is a pangram.
strings
easy
ETL
We are going to do the `Transform` step of an Extract-Transform-Load.
dictionaries
lists
transforming
easy
Raindrops
Convert a number to a string, the contents of which depend on the number's factors.
filtering
strings
easy
Binary Search
Implement a binary search algorithm.
arrays
searching
easy
Phone Number
Clean up user-entered phone numbers so that they can be sent SMS messages.
parsing
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
Scrabble Score
Given a word, compute the scrabble score for that word.
transforming
easy
Proverb
For want of a horseshoe nail, a kingdom was lost, or so the saying goes. Output the full text of this proverbial rhyme.
algorithms
strings
easy
Protein Translation
Translate RNA sequences into proteins.
lists
strings
transforming
easy
Error Handling
Implement various kinds of error handling and resource management
exception handling
easy
Perfect Numbers
Determine if a number is perfect, abundant, or deficient based on Nicomachus' (60 - 120 CE) classification scheme for natural numbers.
integers
math
easy
Triangle
Determine if a triangle is equilateral, isosceles, or scalene.
enumerations
integers
easy
Beer Song
Produce the lyrics to that beloved classic, that field-trip favorite: 99 Bottles of Beer on the Wall.
algorithms
strings
easy
Sieve
Use the Sieve of Eratosthenes to find all the primes from 2 up to a given number.
filtering
math
easy
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.
classes
easy
Robot Simulator
Write a robot simulator.
classes
enumerations
easy
Isogram
Determine if a word or phrase is an isogram.
filtering
strings
easy
Secret Handshake
Given a decimal number, convert it to the appropriate sequence of events for a secret handshake.
arrays
bitwise operations
easy
Kindergarten Garden
Given a diagram, determine which plants each child in the kindergarten class is responsible for.
enumerations
parsing
medium
Saddle Points
Detect saddle points in a matrix.
arrays
matrices
tuples
medium
Bank Account
Simulate a bank account supporting opening/closing, withdraws, and deposits of money. Watch out for concurrent transactions!
classes
concurrency
medium
Acronym
Convert a long phrase to its acronym
strings
transforming
medium
Simple Linked List
Write a simple linked list implementation that uses Elements and a List
classes
lists
medium
Matrix
Given a string representing a matrix of numbers, return the rows and columns of that matrix.
matrices
parsing
medium
Largest Series Product
Given a string of digits, calculate the largest product for a contiguous substring of digits of length n.
integers
strings
transforming
math
medium
House
Output the nursery rhyme 'This is the House that Jack Built'.
algorithms
strings
medium
Pythagorean Triplet
There exists exactly one Pythagorean triplet for which a + b + c = 1000. Find the product a * b * c.
integers
overloading
math
medium
Twelve Days
Output the lyrics to 'The Twelve Days of Christmas'
algorithms
strings
medium
Anagram
Given a word and a list of possible anagrams, select the correct sublist.
filtering
strings
medium
Word Count
Given a phrase, count the occurrences of each word in that phrase.
dictionaries
strings
transforming
medium
Prime Factors
Compute the prime factors of a given natural number.
integers
math
medium
Meetup
Calculate the date of meetups.
dates
medium
All Your Base
Convert a number, represented as a sequence of digits in one base, to any other base.
integers
transforming
math
medium
Pascal's Triangle
Compute Pascal's triangle up to a given number of rows.
arrays
math
loops
medium
ISBN Verifier
Check if a given string is a valid ISBN-10 number.
conditionals
loops
pattern matching
strings
medium
Markdown
Refactor a Markdown parser
parsing
refactoring
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
List Ops
Implement basic list operations
lists
recursion
medium
Simple Cipher
Implement a simple shift cipher like Caesar and a more secure substitution cipher
algorithms
strings
transforming
medium
Roman Numerals
Write a function to convert from normal numbers to Roman Numerals.
transforming
loops
medium
Flatten Array
Take a nested list and return a single list with all values except nil/null
lists
recursion
medium
Binary Search Tree
Insert and search for numbers in a binary tree.
searching
trees
medium
Minesweeper
Add the numbers to a minesweeper board
parsing
transforming
medium
Parallel Letter Frequency
Count the frequency of letters in texts using parallel computation.
dictionaries
transforming
parallelism
medium
Atbash Cipher
Create an implementation of the atbash cipher, an ancient encryption system created in the Middle East.
algorithms
strings
transforming
medium
Food Chain
Generate the lyrics of the song 'I Know an Old Lady Who Swallowed a Fly'
algorithms
strings
medium
Grep
Search a file for lines matching a regular expression pattern. Return the line number and contents of each matching line.
files
searching
strings
medium
Sublist
Write a function to determine if a list is a sublist of another list.
lists
medium
Tree Building
Refactor a tree building algorithm.
refactoring
trees
medium
Scale Generator
Generate musical scales, given a starting note and a set of intervals.
algorithms
parsing
medium
Linked List
Implement a doubly linked list
classes
lists
medium
Crypto Square
Implement the classic method for composing secret messages called a square code.
algorithms
strings
transforming
medium
Ledger
Refactor a ledger printer.
globalization
refactoring
strings
medium
Custom Set
Create a custom set type.
sets
medium
DOT DSL
Write a Domain Specific Language similar to the Graphviz dot language
classes
domain specific languages
equality
medium
OCR Numbers
Given a 3 x 4 grid of pipes, underscores, and spaces, determine which number is represented, or whether it is garbled.
parsing
pattern recognition
medium
Luhn
Given a number determine whether or not it is valid per the Luhn formula.
algorithms
strings
transforming
medium
Run Length Encoding
Implement run-length encoding and decoding.
algorithms
transforming
medium
Yacht
Score a single throw of dice in the game Yacht
games
parsing
sorting
medium
Word Search
Create a program to solve a word search puzzle.
searching
tuples
medium
Bowling
Score a bowling game
algorithms
loops
medium
Transpose
Take input text and output it transposed.
strings
transforming
medium
Nth Prime
Given a number n, determine what the nth prime is.
math
medium
Pig Latin
Implement a program that translates from English to Pig Latin
strings
transforming
medium
Rail Fence Cipher
Implement encoding and decoding for the rail fence cipher.
algorithms
strings
transforming
medium
Change
Correctly determine change to be given using the least number of coins
arrays
integers
medium
Palindrome Products
Detect palindrome products in a given range.
algorithms
strings
tuples
math
medium
Complex Numbers
Implement complex numbers.
tuples
math
medium
Poker
Pick the best hand(s) from a list of poker hands.
games
parsing
sorting
medium
Diffie Hellman
Diffie-Hellman key exchange.
algorithms
integers
transforming
math
medium
Rectangles
Count the rectangles in an ASCII diagram.
parsing
transforming
medium
Wordy
Parse and evaluate simple math word problems returning the answer as an integer.
parsing
strings
transforming
hard
Zebra Puzzle
Solve the zebra puzzle.
logic
hard
Hangman
Implement the logic of the hangman game using functional reactive programming.
events
reactive programming
hard
Diamond
Given a letter, print a diamond starting with 'A' with the supplied letter at the widest point.
algorithms
strings
hard
Two Bucket
Given two buckets of different size, demonstrate how to measure an exact number of liters.
logic
hard
Connect
Compute the result for a game of Hex / Polygon
parsing
transforming
hard
Say
Given a number from 0 to 999,999,999,999, spell out that number in English.
strings
transforming
hard
React
Implement a basic reactive system.
classes
events
reactive programming
hard
Go Counting
Count the scored points on a Go board.
optional values
parsing
tuples
hard
SGF Parsing
Parsing a Smart Game Format string.
parsing
transforming
hard
Zipper
Creating a zipper for a binary tree.
recursion
searching
trees
hard
Alphametics
Write a function to solve alphametics puzzles.
dictionaries
parsing
hard
POV
Reparent a graph on a selected node
graphs
recursion
searching
medium
Rest API
Implement a RESTful API for tracking IOUs.
json
parsing
medium
Affine Cipher
Create an implementation of the Affine cipher, an ancient encryption algorithm from the Middle East.
cryptography
math
strings
easy
Darts
Write a function that returns the earned points in a single toss of a Darts game
floating point numbers
math
easy
D&D Character
Randomly generate Dungeons & Dragons characters
randomness