Sign up
Log in
Home
Language tracks
PHP track
Exercises
Exercises on the PHP track
Join the PHP Track
66 exercises to help you master PHP
easy
Hello World
The classical introductory exercise. Just say "Hello, World!"
optional values
text formatting
easy
Hamming
Calculate the Hamming difference between two DNA strands.
filtering
strings
easy
Gigasecond
Given a moment, determine the moment that would be after a gigasecond has passed.
dates
medium
Bob
Bob is a lackadaisical teenager. In conversation, his responses are very limited.
control flow if else statements
strings
easy
RNA Transcription
Given a DNA strand, return its RNA Complement Transcription.
strings
transforming
medium
Luhn
Given a number determine whether or not it is valid per the Luhn formula.
misc
medium
Isogram
Determine if a word or phrase is an isogram.
filtering
strings
easy
Robot Name
Manage robot factory settings.
classes
randomness
strings
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
medium
Grade School
Given students' names along with the grade that they are in, create a roster for the school
arrays
easy
Robot Simulator
Write a robot simulator.
oop
medium
Run Length Encoding
Implement run-length encoding and decoding.
algorithms
strings
text formatting
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
easy
Raindrops
Convert a number to a string, the content of which depends on the number's factors.
filtering
text formatting
medium
Pangram
Determine if a sentence is a pangram.
strings
medium
Roman Numerals
Write a function to convert from normal numbers to Roman Numerals.
control flow loops
transforming
easy
Sieve
Use the Sieve of Eratosthenes to find all the primes from 2 up to a given number.
filtering
math
medium
Pig Latin
Implement a program that translates from English to Pig Latin
strings
transforming
easy
Leap
Given a year, report if it is a leap year.
integers
easy
Word Count
Given a phrase, count the occurrences of each word in that phrase.
dictionaries
strings
transforming
easy
Anagram
Given a word and a list of possible anagrams, select the correct sublist.
filtering
strings
easy
Trinary
Convert a trinary number, represented as a string (e.g. '102012'), to its decimal equivalent using first principles.
math
easy
Bowling
Score a bowling game
algorithms
control flow loops
easy
Clock
Implement a clock that handles times without dates.
structural equality
time
easy
Wordy
Parse and evaluate simple math word problems returning the answer as an integer.
parsing
strings
transforming
easy
Connect
Compute the result for a game of Hex / Polygon
misc
easy
Minesweeper
Add the numbers to a minesweeper board
parsing
transforming
easy
Change
Correctly determine change to be given using the least number of coins
arrays
integers
easy
Phone Number
Clean up user-entered phone numbers so that they can be sent SMS messages.
parsing
transforming
easy
Beer Song
Produce the lyrics to that beloved classic, that field-trip favorite: 99 Bottles of Beer on the Wall.
algorithms
text formatting
easy
Atbash Cipher
Create an implementation of the atbash cipher, an ancient encryption system created in the Middle East.
algorithms
strings
transforming
easy
Matching Brackets
Make sure the brackets and braces all match.
parsing
strings
easy
Binary
Convert a binary number, represented as a string (e.g. '101010'), to its decimal equivalent using first principles
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.
extension methods
sequences
transforming
easy
Variable Length Quantity
Implement variable length quantity encoding and decoding.
algorithms
bitwise operations
easy
Acronym
Convert a long phrase to its acronym
strings
transforming
easy
Nucleotide Count
Given a DNA string, compute how many times each nucleotide occurs in the string.
dictionaries
strings
easy
Triangle
Determine if a triangle is equilateral, isosceles, or scalene.
enumerations
integers
easy
ETL
We are going to do the `Transform` step of an Extract-Transform-Load.
dictionaries
lists
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
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
Markdown
Refactor a Markdown parser
refactoring
easy
Grains
Calculate the number of grains of wheat on a chessboard given that the number on each square doubles.
algorithms
floating point numbers
easy
OCR Numbers
Given a 3 x 4 grid of pipes, underscores, and spaces, determine which number is represented, or whether it is garbled.
algorithms
strings
transforming
easy
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.
algorithms
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.
integers
easy
Scrabble Score
Given a word, compute the scrabble score for that word.
control flow loops
integers
strings
easy
Perfect Numbers
Determine if a number is perfect, abundant, or deficient based on Nicomachus' (60 - 120 CE) classification scheme for natural numbers.
math
easy
Sum Of Multiples
Given a number, find the sum of all the multiples of particular numbers up to but not including that number.
math
easy
Pascal's Triangle
Compute Pascal's triangle up to a given number of rows.
math
easy
Nth Prime
Given a number n, determine what the nth prime is.
math
easy
Binary Search
Implement a binary search algorithm.
misc
easy
Prime Factors
Compute the prime factors of a given natural number.
math
easy
Flatten Array
Take a nested list and return a single list with all values except nil/null
arrays
easy
Collatz Conjecture
Calculate the number of steps to reach 1 using the Collatz conjecture
algorithms
control flow conditionals
control flow loops
integers
math
easy
Crypto Square
Implement the classic method for composing secret messages called a square code.
misc
easy
Series
Given a string of digits, output all the contiguous substrings of length `n` in that string.
misc
easy
Transpose
Take input text and output it transposed.
arrays
lists
loops
matrices
strings
text formatting
easy
Meetup
Calculate the date of meetups.
misc
easy
All Your Base
Convert a number, represented as a sequence of digits in one base, to any other base.
math
medium
Palindrome Products
Detect palindrome products in a given range.
algorithms
math
easy
Rail Fence Cipher
Implement encoding and decoding for the rail fence cipher.
algorithms
cryptography
lists
text formatting
easy
Affine Cipher
Create an implementation of the Affine cipher, an ancient encryption algorithm from the Middle East.
cryptography
math
strings
easy
Diamond
Given a letter, print a diamond starting with 'A' with the supplied letter at the widest point.
lists
loops
strings
easy
Two Fer
Create a sentence of the form "One for X, one for me."
strings
easy
Armstrong Numbers
Determine if a number is an Armstrong number
algorithms
math