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Computer Science by Example

Welcome to Computer Science by Example! Here you can learn computer programming through a series of exercises. Each exercise is built on top of the previous applying a new concept.

To work on the exercises, you will need:

a desktop or laptop computer with a keyboard and a screen;
a compiler or interpreter for your programming language of choice; and
your brain.

If you need help, read the Computer Science by Example book online.

If you are a lecturer/professor/instructor/teacher, you can use the collection of exercises provided here as part of your teaching material in a programming module/course. See the relevant question in the FAQ for details of how.

Exercise Index

The exercise index is divided into volumes and chapters matching the Computer Science by Example book. After solving each of the exercises, you are invited to submit your solution to an automated online judge which will give you a score and track your progress through your very own user page. Try to get a 1/1 score before moving to the next exercise.

The online judge supports solutions in: Python, C, Haskell, C++, C#, Java, JavaScript, Lua, Ruby, Racket or Scheme.

Volume 1: Programming and Algorithms

This first volume of exercises introduces programming and algorithms.

3. Programming Basics

Exercises in this chapter introduce basic programming concepts, such as: printing and reading from standard I/O, functions, number operations, conditionals and repetition. Beginner programmers can use this chapter to learn their first programming language. Experienced programmers can use this chapter to learn a new programming language.

hello — writing to the screen
cscx — writing to the screen
repeat1 — reading and writing of integers
hi1 — reading and writing of strings of characters
age1 — reading and writing of integers and strings of characters
swap1 — reading and writing of integers and strings of characters
triple1 — functions and integer operations
inc1 — functions and integer operations
add1 — functions and integer operations
mult1 — functions and integer operations
box1 — functions and integer operations
oddeven1 — conditionals (if)
order1 — conditionals (if)
good1 — conditionals (if-else-if)
signum1 — conditionals (if-else-if)
triangle1 — a geometry challenge
factorial1 — recursion
power1 — recursion
fibonacci1 — recursion
hello2 — repetition and loops
total — repetition and loops
countdown1 — repetition and loops
seq1 — repetition and loops

4. Programming

Exercises in this chapter involve fundamental programming concepts. Some exercises are more challenging versions of exercises from previous chapter. Beginner programmers can use this chapter to improve their programming skills. Experienced programmers can use this chapter while learning a new programming language.

repeat — repetition, loops and detecting EOF
hi — reading from standard input
age — reading and writing variables
swap — reading and writing variables
owes — reading and writing variables
triple — functions and integer operations
inc — functions and integer operations
add — functions and integer operations
mult — functions and integer operations
pi — floating point numbers
box — floating point numbers
oddeven — conditionals (if)
order — conditionals (if)
good — conditionals (if-else-if)
bmi — conditionals (if-else-if)
triangle — a challenge
calc — conditionals (case)
factorial — recursion
power — recursion
fibonacci — recursion
index-string — string indexing
repeat-list — lists
index-ints — list indexing
replace — list modification

5. Mathematical Foundations

Exercises in this chapter involve the mathematical foundations of Computer Science: positional numeral systems, logic and boolean algebra, sets and relations. These exercises can be used both as an introduction to these topics or as additional exercises by students working through an academic module.

digit-sum — decimal digits
digit-count — decimal digits
digit-reverse — decimal digits
digit-palindrome — decimal digits
bin2dec — binary digits (bits)
dec2bin — binary digits (bits)
hex2dec — hexadecimal digits
dec2hex — hexadecimal digits
base2base — digits in any base
bool-not — boolean negation
bool-and-or — boolean conjunction and disjunction
discount — boolean expressions
timetable — boolean expressions
intersect — boolean expressions
bool-calc — boolean operations
set-member — set membership
set-ui — set union and intersection
set-calc — set operations
set-size — set cardinality

6. Algorithms

Exercises in this chapter involve the implementation of some common and basic algorithms.

gcd — greatest common divisor
lcm — least common multiple
roundiv — rounded division of integers
primes — finding primes
cash — minimizing banknotes, change-making problem
max-subarray — maximum subarray
sorting — sorting arrays
(More to be added.)

7. Computer Foundations

Exercises in this chapter involve practical computer foundations used in system’s programming.

file-write — writing to files
file-read — reading from files
run-count — file I/O
hello-cmd — handling command line arguments
erro — error output
errxit — controlling the exit code
bytes2bits — bytes to bits
bits2bytes — bits to byte
kilobytes — byte conversions
bconv — byte conversions
file-size — computing the file size
hconv — hertz conversions
(More to be added.)

8. Advanced Programming

To be added.

9. Computational Complexity

To be added.

Bonus exercises

function1 — function from points
function — function from points
ordinal — formatting ordinal abbreviations
rectangle — classes / structured data
apply — functional values / callbacks
rot13 — ROT13 encryption and decryption
caesar — Caesar cypher
brutus — Brute-forcing the Caesar cypher
stack — implementing a stack
queue — implementing a queue
rel-ltom — relation representation
rel-mtol — relation representation
rel-member — relation membership
rel-properties — relation properties
rel-composition — relation composition

About

Email: rudy [at] cscx [dot] org

I am interested in publishing a print book and ebook following the exercises presented here. The first 4 chapters are currently freely available online. If you are an editor and like the idea, contact me at rudy [at] cscx [dot] org.

If you find errors on the website like broken links, typos or incorrect/ambiguous exercise descriptions, feel free to mail me at rudy [at] cscx [dot] org.

The exercises here assume secondary education knowledge (High School / ages 17 and up). However, younger students who have not completed secondary education but are interested in programming may also benefit from these exercises (ages 13 and up).

CScx is not the first of its kind: there are other websites with online programming exercises dating back to at least 1995. However, most online judges are focused on competitive programming problems. Here on CScx the focus is rather on introducing programming step by step with exercises of incremental difficulty.

More exercises will be added in the future, for example, on the topics of data structures and graphs. I may potentially release the exercise test sets for educational use in the future. This way, teachers, lecturers and professors teaching programming and CS modules will be able to run their own exercise sets.

CScx is powered by Udge Online Judge.

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