Follow us on OnTheRoad!

As you already know (Codility heading for US) Codility is on the business development tour in US. You can follow our regular updates on Twitter (@codility) and on OnTheRoad's TripBook (http://codility.ontheroad.to/). Feel free to approach us :)!

Empty sum

User freespace tweets, referring to formulation of our free demo task:

@Codility your equivalent point definition is broken. The left hand sum is from i=0 to k-1, and you have k=0 is a valid solution... [link] ... therefore, the left hand sum is from 0 to -1, and is invalid. You guys can learn a thing or two from reading ACM problems [link]

Having worked a lot on ACM problems, we would have not written this blog post, if not the last sentence, thanks for getting us going! :-) The author of the tweet refers to this expression: which is another way of writing this summation: He/she claims that the above expression is ill-defined for k=0. Let's look into The Holy Scripture, chapter 1.2.3 Sums and Products, verse 1: Clearly, when no integer i satisfies the condition 0<=i<=k-1 (which is written here in an alternate form mentioned by The Scripture, namely i=0 in subscript and k-1 in superscript), we end up with a sum of an empty sequence, which Master Donald Knuth assumes to be equal zero (and we additionally restate the latter assumption in the problem description). So for k=0 the (empty) sum is well-defined and equals 0.

Codility heading for US

Codility is heading for US! Both coasts! We plan to visit New York City, Silicon Valley and Boston, come to meet us at startup2startup or get in touch by e-mail, so that we can book time to meet you in person. Be quick, some slots already taken! (See below.)

Codility in StackOverflow podcast

Joel Spolsky and Jeff Atwood discuss Codility in Issue #79 of StackOverflow podcast series. Tune in at 01:07:30 or have a glimpse at the transcript.

Codility on Hacker News

Hacker News, a discussion board of Y Combinator, held a great discussion on Codility yesterday, go and see for yourself! Big thanks to the Hacker News community for criticism, ideas and bug reports, especially we are indebted to kbob, jkkramer and meilto!