More stupid commercial journal publisher tricks: Wiley won't honor my institutional subscription unless I enable third-party cookies in my browser. So I can (1) decrease my browser security on all sites (2) not read papers by László Babai on J. Graph Theory, (3) ask my librarian for a copy, making much more work and delay for all but maybe letting the publisher know how much negative value-added they're providing, or (4) become a pirate.

Sci-Hub ( to the rescue! Yo ho!

Apparently UNESCO officially decided that March 14 (also known as π Day) would be the International Day of Mathematics. Long live maths! Here is the website of this special day:

My student Matthias Reichinger finished his bachelor thesis titled "Ranking Job Opportunities in a Personalised Career Recommendation System". For me, it was a nice experience to get in touch again with some applied Data Science and Machine Learning techniques.

Congratulations for graduating, Matthias!

Today at lunch, I've learned about the Trash Compaction problem: Can you push objects on a grid into the compact shape of a rectangle if you're only allowed to push all objects from one side simultaneously. Akitaya, Aloupis, Löffler, and Rounds showed that the problem is NP-complete.

The fun variant of this problem talks about pushing around coconuts with a giant coconut pusher... Here are some neat slides:

Our paper for the upcoming SODA is now on :

We give an improved algorithm for computing the vertex connectivity of a graph. At its core, we developed a new local procedure for finding bounded-size cuts containing a seed vertex. Using this procedure, we also improve upon property testing problems, like testing whether a graph is k-edge or k-vertex connected.

Joint work with Danupon Nanongkai, Thatchaphol Saranurak, Liu Yang, Sorrachai Yingchareonthawornchai. has finally been [properly] replaced with

It's a site, based on Laravel, providing CC0 and public domain SVG files, including the 55,000+ we scraped from

#openclipart #svg #inkscape

New online journal Advances in Combinatorics launches:

Like the earlier journal Discrete Analysis (and the technical part of CACM), every paper comes with a one-page overview by the editors explaining the significance of the result in more general terms.

For the journal itself and its five inaugural papers, see

Today I taught my second class on sorting for non-cs students. We mainly worked with playing cards.

Next up is graph traversal (DFS, BFS). Not sure yet, how to teach it, but I thought about discussing strategies for orientation in a maze.

Hi! My name is Sebastian. I'm a computer scientist working on graph algorithms, mainly from the theoretical side. I'm employed by the University of Salzburg, Austria. Currently, my main research interests are dynamic and distributed .


A Mastodon instance for maths people. The kind of people who make \(\pi z^2 \times a\) jokes. Use \( and \) for inline LaTeX, and \[ and \] for display mode.