Codeforces Round 277.5 (Div. 2) grinds

Low-quality and many FST are not a reason of unrated at all. Copied problem may be a reason of unrated — if it afftected a contest a lot.

What matters in this contest is unproved problem — if all problem have non-random solution or random solution having probability of being wrong in low enough and there is no error in testcases which used in the contest, the contest would be rated. Otherwise, the contest should be unrated.

Solving A in 00:00 and 10 unsuccessful hacking attempt ending :P

Do I get TON

Because current F was originally in C — you and the setter had same thought :P

When I started testing, C and D1 were not in the problemset and the order of other problems was A — B — F — E — D2 — G — H. Of course the standing page was funny, and current problemset is even much improvement. This is why I felt lol after testing.

I felt something like lol after testing.

Hahaha as a tester I cannot say about that now, but good luck if you participate!

Tester is me

Now it got *1700 rating tag.

Goal: Reach Grandmaster

Achieve date: 12/31

Yay

Well, there were some contests which suffered such behavior. But were these contests regarded as essentially bad contest?

The scoreboard and predictor says the rating of C would be about *1600/*1700. This difficulty is really not strange and there are a lot of problem C with this rating.

About solution leakage, unfortunately I didn't heard about that, but even if that is true, what does that have to do with the competition being bad? Just that behavior is bad, right?

YES.

1621D - The Winter Hike, 1638D - Big Brush

1704D - Magical Array, 1704E - Count Seconds

1707B - Difference Array, 1710B - Rain, 1718C - Tonya and Burenka-179

1733C - Parity Shuffle Sorting, 1733E - Conveyor <- The author is me, but I thought it is great problem XD.

1746D - Paths on the Tree, 1746E1 - Joking (Easy Version)

1770D - Koxia and Game, 1770E - Koxia and Tree

We have to see all prime numbers less than or equal to n/2. For some prime number p, get the remainder of each element divided by p, and if every number between 0 and p-1 appears twice or more, the answer is NO. If no such prime number exists, the answer is YES. Consider this case,

whatever the value of x is, there should be always 2 multiple of 3, so the answer is NO. Your code print YES in this case.

Why such a bad comment in New Year? To be more precise, what's bad with this contest? I disagree that the contest is bad.

Thanks for the round! Regardless of my performance, I think the problems are nice, especially D and E. This is my short comment for the problems.

A. Normal problem. I used priority queue in D2A for the first time(although naive works) XD

B. Constructive problem. It requires some observation(and maybe some intuition?), normal problem.

C. It requires some intuition again :P, but good problem. I got WA on last pretest because I mistook the limit of n as 50. XD

D. Nice problem. Graph modeling and following observations are good. I heard the implementation can be hard according to approach, but easy implementation exists.

E. Nice problem. The idea is hard, but clear. How to create such problem?

F. I read it, but currently has no idea.

G, H. Not read.

My performance in Good Bye 20xx contest has many ups and downs, this time my performance went up, maybe I can reach GM for the first time?

So G has 3 subtasks? XD

Thanks for the great round! How to solve F?

No, of course.

I can tell it here. Do you want to know?

As a guest setter and tester, I leave no comment about the round.

If you experienced global round many times, you will never think like that. A global round always taught in a painful way.

And I don't know why many FSTs of B matter. Making strong pretests is obviously good to participants, but it is not mandatory. Sometimes FSTs are needed for participants to implement more error-freely and accurately. This time I failed D in system testing, but I don't blame setters.

FST means that a participant wrote wrong code, so that participant should be held accountable for the wrong code. But I often feels this fault is completely overshadowed and only setters are blamed. Isn't it?

I cannot understand why this blog gets many downvotes.

But I passed B and failed D XD

Many failed system test in B

Is F easier than E? I found there are many participants who solved F much faster than E.

Edited. Thanks!

Well, standing says it can be easier than *1500. It is what I estimated before the contest, maybe real difficulty is more easier? :/

It is one of the result of an observation. To do such observation, check if it can be transformed to be structurally identical.

I don't know.

I think *1500.

Now editorial is available.

Edited, thanks. There was some mistake while translating 0-based MCS into 1-based editorial.

We estimated A as *800, B as *1000 or *1100. Let's wait.

i is correct. Now edited. Thanks for noticing me.

Yes.

Edited the phrase more clearly.

Yaay

Thanks for enjoying! Actually, some testers gave O(n) solution of D2 already, but we decided to accept O(n^2) solution for difficulty balance.

Sorry for that. The constraint changed just before the contest start, and it seems to have taken some time to reflect on the problem page.

I didn't notice that until I see this comment

I wanted to participate in the contest, but skipped. When morning came, I heard the contest has become unrated? :/

Good

Well, is stating some facts allowed? I think it isn't.

But why do you talk about problems here? The contest is running now anyway.

Problems are not bad, but the problemset is too hard :(

Thanks for the round! I think the problems are interesting.

My comments for each problem:

A. Not bad, but quite implementation-based problem. Unfortunately, I got FST. XD

B. Fine. It seems there are some hack on this problem.

C. Today I became second-solver of C. Yay!

D. Quite interesting.

E. How to solve it?

F. Read, but didn't thought deeply about it.

Also, I think the gap between C-D-E is a bit large.

XD

I don't know what to say about this round. I just appreciate that I don't feel bad although I performed poorly.

I also solved C by this way. Actually, I thought it was intended solution during contest XD

1-gon's first round got unrated due to the long queue. Now Asymmetry and Markadiusz set their first round coordinated by 1-gon, and the round got unrated due to the long queue. RIP

Thanks for the round and fast editorial.

If we convert double to long long, the fractional part would be discarded. So in this kind of problem, if we add small real number and convert it, we can see the same effect as rounding.

Will be rated.

If I could say..

"100000110100(2100) = 2100**11 + 2100**5 + 2100**4 + 2100**2 ~= 3.5e36. Now we are all rated, so yay!"

+Have Some Fun

What do you do when your friends do not lock their laptops?

Well, it seems there is some disrespectful comments. Please respect the setter. For me C was good problem, and although I couldn't solve, E was also interesting. Thanks for the contest.

Thanks for a nice extension! However, when I opened the profile of vjudge3, data loading was not completed even after a few minutes XD

Well, I have seen a participant in situation like this, and he said 404 Error was displayed when contest started :D

It was very memorable round.

The most pretests I have seen

One more FST :D

Only once I saw this score

The approach of problem D is similar with 1406D - Three Sequences, 1442A - Extreme Subtraction.

Couldn't submit 1B by 10 seconds :(

Thanks for the round. I think the problems were good, except A. The sad thing is that the gap between D and E was large.

Oh, that makes sence.

Score distribution says the total score of E is 3000, whereas the score of F is 2000. Does this mean E2 is harder than F? Interesting.

Editorial also says stack solution. I think just greedy approach can reach this solution.

Well, to be honest, I think C is quite boring problem. Although I didn't think the statement of C is bad during the contest, it seemed just another basic stack problem anyway.

The gap between C and {D, E} is too large :(

The setters wanted to emphasize "Problem C uses constructive algorithms" (Some other problems also have two same tags)

lol, how to do well in global round? Weirdly I perform badly whenever I participate in global round(somewhat not bad in other Div. 1 + Div. 2 round).

That input means 'After reading all input, then print all output, including empty line.'

Basically, if you match the sample output and sample input, you can see that it is a perfect fit.

Empty lines in sample exist to distinguish the order of input and output. Not a mistake.

There is a word "Constraints" instead of "Output" in problem A.

See this.

Codeforces Round #709 (Div.1 only)

I did the same thing and gained -50 points. My bad :(

Only one color in the first AC :D

How to solve C?

First time to see '5000' in the score distribution

New difficulty staircases with a wall

More, 1E had 95 pretests but not good efficiency.

How to solve E?

How to solve E?

Just asking, did the testers give no feedback about the difficulty? It would be much better if there were one more problem between A and B.

1316C - Primitive Primes

1334E - Divisor Paths

1408F - Two Different

1451E2 - Bitwise Queries (Hard Version)

Almost same problem with this — 1153C - Serval and Parenthesis Sequence

Parade of Invalid input in A XD

.

It seems someone uphacked an accepted code after finishing system testing. There is no error.

codeforces's new record

This is really tough problemset :|

It seems, your code initializes $$$M$$$ only once, and in the loop the previous data is overriding. You need to initialize $$$M$$$ in each testcases.

Even when I saw that comment first time, it already got about 70 downvotes, which made me surprised.

A negative-rating tester whose atcoder rating is more than 2000 :D