Thanks for your suggestion! I’ll fix problem D examples soon. You said move D further into the problemset, so what you meant is move it to like problem E or F? Btw, actually I think I’ll remove problem D as it’s quite weird actually, replace it with another problem.

Thanks for your correction!

Yeah you’re absolutely right! My concern is that many beginners don’t know what is modulo arithmetic and some properties (like (a + b) mod n = (a mod n + b mod n) mod n). So I decided to use int128. But yeah, you’re right cuz int128 may cause unexpected errors. I’m planning to replace it to another problem in the future.

Yeah the contest will be in IOI-style, there will be multiple test cases for each subtask.

Yea I'm planning to cancel them too. But maybe some students were really weak (don't even know how to write modulo) and i decided to give some mercy to them lol :)

Auto comment: topic has been updated by jonahgamer110 (previous revision, new revision, compare).

Auto comment: topic has been updated by jonahgamer110 (previous revision, new revision, compare).

When your approach is a bit off track then you'll get wrong answer. This is why I don't like this problem.

I'm sorry I think i should describe it as "The edge cases are too hard to find". The problem is that I really don't know where did I do wrong and it becomes super annoying. There are a lot of test cases but only 1 or 2 of them are strong. You can observe that there are many people attemped the problem but did not get AC.

To be honest, I really don't like C. There are too many edge cases and I got 8 Wrong Answers but still didn't solve

Basically, you can stack the arrays in any order and the arrays must be left-aligned (A longer array on top of a shorter one is also ok). Then, elements in each array will fall down until it touches another element (In other words, no elements are "floating"). Finally, get the elements at the bottom of the stack from left to right and form an array. Let the array be a, your task is to find the lexicographically smallest a.

Noooo i did so well and it became unrated sad. Anyways still a good round

Nice contest! Best description and questions comparing with the few past contests! Problems are clear and fresh to look at. I solved 5 problems and a bit regret to register unrated. (Although I'll still lose rating if it's rated lol)

Got stuck in problem B for five tries until I found that I input k and j in the wrong order OMFGGGG!!!! (At 2 hours :)) Never done such stupid thing before!!

Anyways, good contest and looking forward for the editorial!

UPD: Super quick editorial out yay :)

You can use dfs to traverse and maintain a bool dir (direction of the edge). Keep changing the dir when having a dfs traversal. However, if you meet a node with degree = 2, you do it special for once only (It will cause an increase of 3 in answer with two edges costed. As there are n — 3 edges left, the answer will be exactly n)

Here is my submission: 325811538 (I did check for the starting node to be degree = 1 then do dfs but that's unnecessary, just did it for safe)

As a specialist, I was cooked!

Ohhh I finally understand now!! Thanks for your patience for teaching me!

Here are some similar problems that I think they are interesting (Did them before during previous contests):

Easier problems:

https://codeforces.me/problemset/problem/2093/C (Number theory and math)

https://codeforces.me/problemset/problem/2071/B (Math)

Harder problems:

https://codeforces.me/problemset/problem/2104/D (Also GCD)

https://codeforces.me/problemset/problem/2097/A (An interesting math problem)

Yeah me too. I handed in like 7 times and they all got WA in pretest 3. No idea about the edge case.