Overview

This website consists of two parts:

1. the C++ source code of my solutions to more than 300 Project Euler problems
2. about ten PHP scripts to generate HTML code on-the-fly - solely based on the C++ source code !

This enables me to rapidly apply visual and structural changes to my website.

C++ compiler

GCC is my compiler of choice but almost all files can be compiled with Visual C++ or Clang, too.

I decided to settle with C++11 because it's widely supported and there are very few features of C++14/17 that justify switching to those newer standards.
(whenever the code requires C++11 then C++0x is usually fine, too, so GCC 4.7 should be sufficient)

Live Tests

My live-tests are a three-step procedure:

1. filter user input and reject invalid parameters (done in PHP)
2. forward valid input to STDIN, run the program and grab STDOUT (compiled binary)
3. check whether output matches the default answer and suppress it, else return it wrapped in a JSON packet (in PHP)

Markdown Syntax

When you look at the comments of my C++ files then you will notice a few strange symbols: that's Markdown syntax.
For example, a link is described as [my link text](http://myurl.com).

I heavily modified Johnny Broadway's Slimdown class (see this gist at Github) to fit my needs - it's now more than twice as big.
The most important changes are automatic detection of mathematical formulas which will be rendered by KaTeX (see next chapter).

Properly Displayed Mathematical Formulas

The wonderful KaTeX Javascript library renders all formulas.
A bit of PHP processing allows me to use a slightly simplified syntax, e.g. remove the backslash in front of commonly used functions, such as sqrt instead of \sqrt.

I tried MathJax but it was much slower, not even mentioning its huge file size.
My optimized KaTeX distribution needs about 30 kB (minified and compressed) plus a few fonts which are about the size.

C++ Syntax Highlighting

My C++ syntax highlighting is far from perfect but surprisingly simple:
I "stole" quite a substantial amount of ideas from a posting on Dominic Szablewski's blog.

Now about ten regular expressions cover the vast majority of use cases and I can live with a few pitfalls every now and then.
Almost all other syntax highlighting libraries are much, much bigger and have their own shortcomings.

Virtual URLs

None of my website's URLs actually exists. There is no https://euler.stephan-brumme.com/inside/ - but there is lots of URL rewriting happening in the background
that finally executes inside.php (which can't be accessed directly).

This gives me the power to easily control what parts are accessible and which are hidden.
For example, if I solve the most recent problem then I block access until a new problem is published by Project Euler.
And based on my logfile I know that this happens quite frequently ...

Even standard URLs like https://euler.stephan-brumme.com/1/ are rewritten inside the Apache server (mod_rewrite) such that a PHP file is executed with parameter 1 so that 1.cpp will be parsed.

Meta Data

My C++ lack a few things:

• difficulty (in percent)
• allowed input range (for live tests)
• the solution (needed to prevent my program from showing the correct solution right away)

Heatmap

Please click on a problem's number to open my solution to that problem: