I recently solved the follwing problem:
Given a string str, find it's rank in all of it's unique permutations.
Example: str = 'aba'
All unique permutations of aba (in sorted order) = ['aab', 'aba', 'baa']
Hence, the rank is 2.

I was wondering how can we solve the following (relevant) problem:
Given a string str and a rank r, find the permutation of str with given rank r.
So, for input str = 'baa' and r = 2, output will be 'aba'

If there are no repetations in string, I can use

How do I handle repetations?

Hello everyone,

Crack me if you can! was held on Codechef on 05 June, 2020. It was held by a indiviual guy ameya13.

The question set contains 5 questions, out of which one shows wrong output for sample test cases (Tony and the triplets), another one have test cases out of constraints (BT engine) and one question have ambigious statement (Interview Day). I was unable to concentrate to read the last question (Pencryption Password).

There were many high rated participants like Egor, VladProg, alexwice and many other yelow-orange coders of Codechef community. Checkout the standings here.

Now, one noticeable thing is that there are many WA verdicts. (Of course, due wrong test cases). Still, mayur2305 and starkk99 managed to solved them without any wrong submission (also really fast) and got rank one and two respectively. Third rank holder was maoni, and this is his/her first contest using this ID. There are no previous submissions. ID was made for this contest.

Now the thing which bothers me is that organiser ameya13, and rank holders starkk99 and mayur2305 were teammates in many contests. Check here. Moreover starkk99 and organiser ameya13 are from the same college! (starkk99 edited his college information in codechef for this contest.)

I think this much evidence is enough prove that this round was full of cheating. All all this was done for 250 laddus! I request codechef admins and coordinators (vijju123, l_returns) to cancel the laddus for this round.

Any edit suggestions are welcome.

Edit 1: Codechef link of the discussion: here.

Edit 2: Admins decison can be seen here.