### Arpa's blog

By Arpa, history, 3 years ago, , Hello again, It’s Arpa as usual :P. Hope you enjoyed from the Gym, and it’s here is the editorial.

Problem packages are available here. Solutions are available here separately.

## Preparation details:

The problems authored by me when the main contest was authoring. Here is a table, showing the percentage of expected accepts (in my opinion, before the contest) and the number of accepts.

 A B C D Expected 100% 30% 70% 10% Accepted 27 0 8 0

## Difference from main problems

A : n is bigger, binary_pow will not work. You need to calculate in a faster way.

B : n and also numbers are much bigger, simple xor will not work.

C : n is bigger, simple LCM will not work because the answer would become really large.

D : Number of alphabets are 26 instead of 22, so it isn’t possible to allocate an array with size 2z (z = 26).

## Hints

A : Write the last digit of 1378n for several small values. Calculate in a fast way.

B : Note that if then . Use trie.

C : If the answer exists, it depends on the lengths of cycles in the functional graph. Factorize numbers and calculate LCM.

D : Keep a mask for each vertex, i-th bit of maskv is true if the number of edges in the path from the root to v such that letter i is written on them is odd. Now if number of bits in is 0 or 1, path between v and u is Dokhtar-kosh. Give an id to each mask.

## Details

First accepts: A : retired_coder, C : wrinx.

Funniest code : hrzuser ’s code : 23229169. He was managing to get accepted in problem C, with a solution :O.

## Solutions

I’d like to finish the editorial with the below poem by Saadi Shirazi:

مقدار یار همنفس چون من نداند هیچ کس ماهی که بر خشک اوفتد قیمت بداند آب را

Translation: No one knows the value of good friend as I know, fish will know the value of water when it falls on the beach.

Goodbye ; ) Tutorial of Codeforces Round #383 (Hard) gym, Comments (4)
 » Actually there was not defference between easy A and hard A because everyone solved them by the same way
•  » » Well the base concept is the exact same but calculating the mod is different.
 » What is the difference between this D and it's easier version?
•  » » Read the Difference from main problems section.