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Exercises on the Common Lisp track

Join the Common Lisp Track
42 exercises to help you master Common Lisp
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
optional values
text formatting
easy

Hamming

Calculate the Hamming difference between two DNA strands.
control flow conditionals
control flow loops
equality
filtering
strings
easy

RNA Transcription

Given a DNA strand, return its RNA Complement Transcription.
control flow conditionals
strings
transforming
easy

Leap

Given a year, report if it is a leap year.
control flow conditionals
equality
integers
logic
easy

Anagram

Given a word and a list of possible anagrams, select the correct sublist.
equality
filtering
strings
easy

Beer Song

Produce the lyrics to that beloved classic, that field-trip favorite: 99 Bottles of Beer on the Wall.
control flow conditionals
control flow loops
integers
text formatting
easy

Roman Numerals

Write a function to convert from normal numbers to Roman Numerals.
control flow conditionals
control flow loops
integers
strings
text formatting
easy

Word Count

Given a phrase, count the occurrences of each word in that phrase.
control flow conditionals
control flow loops
filtering
strings
easy

Bob

Bob is a lackadaisical teenager. In conversation, his responses are very limited.
control flow conditionals
parsing
strings
medium

Luhn

Given a number determine whether or not it is valid per the Luhn formula.
algorithms
strings
transforming
easy

All Your Base

Convert a number, represented as a sequence of digits in one base, to any other base.
integers
map
math
transforming
easy

Acronym

Convert a long phrase to its acronym
strings
transforming
medium

Twelve Days

Output the lyrics to 'The Twelve Days of Christmas'
algorithms
strings
easy

Sublist

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

Grains

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

Gigasecond

Given a moment, determine the moment that would be after a gigasecond has passed.
date
integers
time
transforming
variables
easy

Robot Name

Manage robot factory settings.
randomness
strings
variables
easy

Raindrops

Convert a number to a string, the content of which depends on the number's factors.
control flow conditionals
filtering
integers
easy

Grade School

Given students' names along with the grade that they are in, create a roster for the school
interfaces
lists
maps
sorting
variables
easy

Phone Number

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

ETL

We are going to do the `Transform` step of an Extract-Transform-Load.
control flow loops
maps
transforming
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
interfaces
transforming
easy

Nucleotide Count

Given a DNA string, compute how many times each nucleotide occurs in the string.
control flow loops
maps
sorting
strings
easy

Collatz Conjecture

Calculate the number of steps to reach 1 using the Collatz conjecture
integer
recursivity
math
easy

Perfect Numbers

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

Isogram

Determine if a word or phrase is an isogram.
strings
easy

Meetup

Calculate the date of meetups.
control flow conditionals
dates
filtering
easy

Triangle

Determine if a triangle is equilateral, isosceles, or scalene.
control flow conditionals
filtering
floating point numbers
integers
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.
control flow loops
floating point numbers
integers
math
easy

Scrabble Score

Given a word, compute the Scrabble score for that word.
control flow loops
games
maps
strings
easy

Binary

Convert a binary number, represented as a string (e.g. '101010'), to its decimal equivalent using first principles
bitwise operations
control flow conditionals
integers
math
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
control flow conditionals
integers
text formatting
easy

Sieve

Use the Sieve of Eratosthenes to find all the primes from 2 up to a given number.
control flow conditionals
control flow loops
filtering
integers
maps
math
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.
control flow conditionals
control flow loops
filtering
sequences
easy

Atbash Cipher

Create an implementation of the atbash cipher, an ancient encryption system created in the Middle East.
control flow conditionals
control flow loops
sequences
transforming
easy

Prime Factors

Compute the prime factors of a given natural number.
control flow conditionals
control flow loops
filtering
integers
maps
math
easy

Crypto Square

Implement the classic method for composing secret messages called a square code.
arrays
control flow conditionals
control flow loops
strings
transforming
easy

Trinary

Convert a trinary number, represented as a string (e.g. '102012'), to its decimal equivalent using first principles.
control flow conditionals
integers
math
easy

Pascal's Triangle

Compute Pascal's triangle up to a given number of rows.
control flow loops
integers
sequences
math
easy

Armstrong Numbers

Determine if a number is an Armstrong number
integers
lists
math
easy

Robot Simulator

Write a robot simulator.
misc