Well the second question bugged me a lot i thought of dp and stuff but brute force worked wasted a lot of time there. The third question was completely implementation based but got wrecked by SIGSEV found the error in the last minute!

My rank is 580. Will my rating increase? ( Not a big deal, but still curious lol )

Each row of the matrix must be a palindrome. So if M is even, every element must have an even number of occurrences. Otherwise, exactly at most N elements must have an odd number of occurrences, the rest even. Constructing it is just placing the even/odd elements appropriately.

I would like to correct you. Not exactly N elements must have odd appearances. It is <= N, because you can take 2 even occurring elements also for the middle element.

Doesnâ€™t it have to be more than that? The first elements that Chef and Chefina write down, respectively, are A_{1, 1} and A_{1, M}. The second elements are A_{1, 2} and A_{1, M - 1}, and so on. So each A_{i, j} must be equal to A_{i, M - j + 1}.

It was good. Had participated in codeforces round just 25 minutes before the Cook Off and that made my brain to hang up but still managed to solve 2 questions.