Hello, Codeforces!

We are glad to invite you to the awesome (we've tried our best to make it such) CodeChef AlgoManiac 2021: Code For Future, brought to you by Chandigarh University and CodeChef, that will start on Thursday, September 02, 2021, at 20:00 IST (UTC + 5.5).

Joining me on the problem setting panel are:

• Contest Admin: nishant403
• Setters: hitch_hiker42, prasanna2425, ars9, ShivY08
• Testers: _runtimeTerror_, nishant403, Vichitr, infinitepro, hitch_hiker42, prasanna2425, ars9, ShivY08
• Editorialist: infinitepro

There will be 8 problems, and 3 hours to solve them. We have made sure the problems are well-distributed across various concepts, such that they are pairwise distinct with respect to the ideas involved. Also, we tried our best to make the problem set balanced so that there is a gradual growth in difficulty (subject to maybe, at most one exception) from one problem to the next. Finally, we made the tests sufficiently strong and the length of the problem statements is kept inversely proportional to the difficulty of the problem.

The contest will follow the rules of ICPC and will be rated for the participants of Division 3. Each problem is binary, which means you will either solve the problem (by passing all test cases across all test files) or fail. There are no subtasks or partial scores. All the problems have the same points allotted to them. Users are ranked according to the most problems solved. Ties will be broken by the total time for each user in ascending order of time. The total time is the sum of the time consumed for each problem solved. The time consumed for a solved problem is the time elapsed from the beginning of the contest to the submission of the first accepted run plus 10 penalty minutes for every previously rejected run for that problem. There is no time consumed for a problem that is not solved.

This is an open contest, and anyone (regardless of age, gender, nationality, etc) can register themselves by going through the contest link. Also, you can learn more about the event and Tech Invent 2021, the annual tech fest of Chandigarh University, the institution that is hosting the contest, along with CodeChef!

Finally, here are the prizes:

• $$$1^{st}$$$ Place: 50,000 INR
• $$$2^{nd}$$$ Place: 30,000 INR
• $$$3^{rd}$$$ Place: 20,000 INR

One final note: remember to read all the problems, and stay plugged in while the adrenaline lasts! Farewell, until we meet again.

Few Updates:

• The contest is going to be rated for the participants of Division 3 (though everyone is eligible for the prizes).

• The time and date of the contest have been updated to avoid a clash with September Long Challenge which will commence two hours before the earlier scheduled time, and because of CodeChef rules, the participants would then had to wait till the end of the Long Challenge for the rating changes.

• The number of problems has been increased from 6 to 8.

There is a class of problems that always bug me:

https://codeforces.net/problemset/problem/1263/A

https://codeforces.net/problemset/problem/1366/A

https://codeforces.net/contest/1539/problem/A

There are things common with these types of problems:

1). they usually require doing greedy casework or edgy math

2). you can sometimes force a binary search solution to pass (though it is tedious)

3). usually given as Div2 A/B (hopefully not in Div1), so you feel a little frustrated after not solving them for around 30 minutes (which sometimes results in a bad contest)

4). most of them are in the difficulty range: 900-1200

5). even after you solve these, there's a little scope for satisfaction

6). I'm a little curious about this one: some of these are written by MikeMirzayanov (probably he can explain better :p)

I hate these problems, probably because I am too lazy to do the casework or I suck at greedy or maybe the sort of math that's involved (eg: ceiling or flooring things, maybe check if the remainder is zero in the end, maybe add 1 or subtract 1?) doesn't suit my taste yet. Do you guys like these sorts of problems? If yes, can you explain what is the motivation behind them, and why you like them? I want to get rid of this feeling and get better at these types of problems.

For context, I was solving this problem: https://cses.fi/problemset/task/1701, and was wondering if we can decompose the two trees into their respective centroid trees, and then compare their Euler tour sequence for bijection.