Tag Archives: LunchTime


CodeChef October Lunchtime

October Lunchtime starts in just under 24 hours, and I am the editorialist for the whole contest.

This time, problems are especially interesting for me. Big thanks to Pavel Sheftelevich, who created all of them. Pavel has a great ability to create incredible problems with really simple statements - the thing we all love. The setter of a previous Lunchtime, Sergey Kulik, is the tester of the whole problem set this time. We started working on this contest later than usual, but it turned out, that a great contest can be prepared in just a few days :)

If you decide to participate, which you should do, you will probably start with solving two simple problems: an easy string problem and an interesting one ad-hoc problem related to multiplication extremely big numbers. For those of you who managed to solve them quickly, there are two harder problems waiting. I can tell you, that a desired solution to one of them uses a technique, which is not known as much as it should be. I will describe the approach with details, in the editorial, which will be posted just after the contest on Codechef discuss. The last subtask to the second of these harder problems, at first time might look unsolvable for some participants, but I really encourage all of you to engage all of your skills to solve it. If you manage it, you will be very pleased :)

See you on Leaderboard!

All editorials are available here


CodeChef September Lunchtime

September Lunchtime starts in under 2 hours, and I am the editorialist for the whole contest.

Problems are exceptionally interesting - big thanks to Sergey Kulik. You will have to deal with fancy pattern matching, some palindroms, maintain a collections of sets, and decide when is it best time to drink a cup o coffee :)

This lunchtime will be probably slightly harder than usual, so I advice to read all the problems very carefully, and stick to the details. Remember, as always on CodeChef, each problem has a few subtasks, and if you do not know how to solve it for the original constraints, we encourage you to solve as many subtasks as you can.

Techniques used it the problems are extremely useful, and I strongly recommend to solve all of them, even after the contest. I hope that my editorial will be helpful to explain intended solutions as well as solutions to each subtask. They will be published just after the contest, so stay tuned :)

UPDATE: All editorials are available here: September Lunch Time Editorials

One more thing worth to mention is that, AngryBacon, who is a tester in the contest, solved one of the problems faster than the indented solution was, so we decided to add another subtask to this problem, with even higher constraints. I am curious if you can spot that subtask during the contest ;)

See you on leaderboards!


CodeChef July LunchTime // Editorialist

The CodeChef July LunchTime begins soon and I am the editorialist for the whole problem set.

The problems are really good and if you decide to take part in it, you won't regret it for sure!

As a quick tip, I can tell you that 3 problems are very cool ad-hook ones - they do not require any specific knowledge, just thinking and coding. The last problem is a math related challenge :)

Good luck!

After the contests I will post the most liked editorial here.


Codechef January Lunchtime from Editorialist

The Codechef January Lunchtime just ended and I was the editorialist for this one. You can find editorials to all 4 problems here:


While 2 problems were quite easy, the other two are very interesting and I had so much fun while solving it, check them out:



Congrats to all participants and let's meet in the next Lunch Time :)