(Amazon links: US,
This web page contains a free electronic version of my self-published textbook Algorithms, along with other lecture notes I have written for various theoretical computer science classes at the University of Illinois, Urbana-Champaign since 1998.
A black-and-white paperback edition of the textbook can be purchased from Amazon for $27.50. The full-color electronic version will remain freely available here indefinitely. (If there is enough demand, I may publish a full-color printed version of the next edition. Color printing is considerably more expensive; a full-color printed version of the current book would cost about $75.)
After years of trying and failing to manage bug reports by email, I now maintain an issue-tracking page at GitHub. If you find an error in the textbook, in the lecture notes, or in any other materials, please submit a bug report. All other feedback is welcome as well.
Anyone is welcome to download, print, use, copy, and/or distribute anything on this page, either electronically or on paper. You do not need to ask my permission, although I would appreciate hearing from you if you find this material useful. If you redistribute any of this material, please include a link back to this web page, either directly or through the mnemomic shortcut http://algorithms.wtf. Specifically:
Please do not ask me for solutions to the exercises. See the course materials page for an explanation.
This material is the primary reference for two regularly-offered theoretical computer science courses at Illinois: CS 374
CS 473. I taught these courses most recently in Spring 2018
and Spring 2017, respectively.
I maintain a complete archive of my past homeworks, exams, and lab handouts on a separate page.
Prerequisites. The textbook assumes knowledge of discrete math (especially induction) and basic data structures and algorithms (especially recursion) consistent with the prerequisite courses CS 173 and CS 225 at Illinois. (See the for more details.) For a thorough overview of prerequisite material, I strongly recommend the following resources:
Get the Book
More Algorithms Lecture Notes
Both the topical coverage (except for flows) and the level of difficulty of the textbook material (mostly) reflect the algorithmic content of CS 374. The remainder of these notes cover either more advanced aspects of topics from the book, or other topics that appear only in our more advanced algorithms class CS 473. Don’t be fooled by the fancy typesetting; these notes are considerably less polished than the textbook.
Models of Computation
These notes cover (a superset of) the automata and formal languages material in CS 374. Some of these notes are a lot more polished than others.
If were not a little mad and generally silly
I should give you my advice upon the subject, willy-nilly;
I should show you in a moment how to grapple with the question,
And you’d really be astonished at the force of my suggestion.
On the subject I shall write you a most valuable letter,
Full of excellent suggestions when I feel a little better,
But at present I’m afraid I am as mad as any hatter,
So I’ll keep ’em to myself, for my opinion doesn’t matter!
It is time we did away with “publish or perish” and replace it with “publish and perish.”
Nothing will be more blasphemous than writing a textbook that anyone can go out and buy.