https://atcoder.jp/contests/arc208/submissions/70095560

Think about $$$\operatorname{xor}$$$ sum of all of these numbers. $$$\operatorname{xor}$$$ sum of the final state is exactly $$$\operatorname{or}$$$ sum of the original state.

I'm the first solve of A!!!

But I can't solve CDE. Too hard. Losing rating again.

My $$$\mathcal O(n\log^2n)$$$ solution for G received TLE.

Did not solve B.

:/

Codeforces is really fast and smooth today. How can you achieve this?

update: Problem F 339613954

-78 rating :(

Dislike most problems. Hard and strange. D<A<B<C.

Almost solved F with some $$$\mathcal O(n\sqrt n)$$$ solution.

I'm losing hundreds of rating. Probably contribution as well.

D is unexpectedly easy.

My friend asked me what is needed for D. After thinking for a while, I told him "a few arrays and variables".

For the 3rd version, $$$\left\lceil\frac n{11}\right\rceil+\left\lceil\log n\right\rceil=101$$$. I generated it through a silly idea. But it's soooooo close to the constraint. Is it intended to stop it from accepted?

Good problems. I enjoy them very much.

But I did very badly. Too slow and too many wa atts. Bye GM.

Problems are interesting and challenging.

However, I performed badly :(

I know, but very often they are almost the same.

wtf a div2 with 3500 problem? Why not add more problems and extend it to a 1+2?

hook->tick

Also although this standard is published by CCF, it's abandoned by itself.

We(luogu) just found it good and use it to measure users' performance in official competitions.

Years has passed and now there are really a large amount of ppl with blue tick or golden tick.

I have to say, usually Luogu div1/2 difficulty >> Codeforces div1/2 difficulty. "similar" is a fake information.

Try 熱中症 lol

B and C are both ez to implement, but need some brave observation(guessing). Like them.

Solved ABD.

Hope I can get positive delta!

Is this rated for 3rd ucup?

In my room

I think I've caught a group of cheating noobs spreading wrong solution of B and giving +100 points to lucky participants.

My team got rk36. I solved AHKNO.

Any official tutorials?

You can't find corners correctly in this way.

F is Mike's idea :O

But I think you can't avoid sort so the time complexity can't be $$$\mathcal O(n)$$$.

My sol for F:

Find all corners. Remove all corners and run the algorithm for a second time to get a second group of corners.

A fountain becomes a new corner (after one of the old corners is removed) if and only if:

• it is among the second group of corners; and
• it is covered by only one corner.

A corner $$$(u,v)$$$ covers the range {$$$(x,y)|x\in[1,u],y\in[v,m]$$$}.

A fountain becomes a new corner after removing the corner covers it.

It's easy to calculate change of area now.

264008397

(Why $$$\{$$$ -> $$${$$$)

Easy problems in abc are designed to require no algorithm but programming language.

AI masters programming languages very well and also know a little about algorithms.

It's normal for AI to solve these problems, or AI would be too weak.

Look at the standings. It seems your F is too hard for a div2 so it works like a 5-problem round. Is that good?

Why are you and Haitang0520 not among them?

I guess in fact they are enumerating $$$i$$$ from $$$n-1$$$ to $$$0$$$ in the sample implementation.

Remind me of this

yes

What about you SkyWave2024? You are using an alt with image and nick similar to another person SkyWave2022 to hide your personal information and attract attention.

How can you write a post? You only have competed three times and solved >=1 problem twice in them. Are you trusted?

1967F - Next and Prev why *3200?

It seems the method here is different.

It's still $$$\mathcal O(n\log^2n)$$$.

We can decompose this problem to "Counting points on a 3D plane".

dfs the whole tree. The i-th visited vertex j is considered to have i-th dfn. i.e. $$$dfn[j]=i$$$.

In this way, a subtree can be represented with a range on dfn. Let $$$sz[i]$$$ be the number of vertexes in i's subtree. i's subtree = $$$[dfn[i],dfn[i]+sz[i])$$$.

I found smth similar to this in your words. Maybe not too many ppl call this "dfn".

It's known that subtree query is weaker than range query and single point modification is weaker than range modification :/

Exactly.

Mathforces.

Weak pretests. Maybe I can get positive delta with points earned by hacking.

It's a stack.

Will zhoukangyang win Turing Cup or will he write the problems?

How hard will this round be? They are known to create hard problems. :/

:O tourist problem

Both the idea and constraints gives me a strange feeling. 1732D2 - Balance (Hard version)

Can't understand your opinion. I don't think you are right.

How can you solve these HARD problems so FAST? negative again:(

What is this 252777884 Pq_oqtg_96VtCmVqT_tqwpfu

For F:

I wrote a $$$\mathcal O(\sum cnt^2_{divisors})$$$ and thought it was brute force but it passed. It can be really short and fast if implemented well.

Why it's the intended solution? $$$n=10^6$$$ usually leads to a $$$\mathcal O(n\log n)$$$ solution.

Anyway, a typical 74 math problem.

That math problem is too hard. Solved it too slowly. I'm losing a lot rating.

These 2250 are slightly eazier than average.

Trash sample.

I'm back, GM.

Why not read his submission 250862298

It's called "Open" instead of "March". Why? Will there be any differences?

Congratulations! You've entered Hall of Fame!

Too hard. Only solved ABC.

Can we solve G with half-plane mo's algorithm? It's not well known I think and I'm unsure how to implement it. I suppose its time complexity is $$$\mathcal O(n\sqrt m)$$$.

GNU C++17(20) also fails. 249014238 Maybe it's related with 64bit platform. int is 32bit. There may be some bugs in the complier dealing with this case, I think.

I've written smth interesting for problem E here.

I think it's the 100th div3.

zhoukangyang will win IOI2024!

Mike is working really hard!

cheater

Fun fact:

• Polygon: 2009-2024
• Codeforces: 2010-2023 (still 2023 when this comment is sent lol)

remove the one with lower contribution lol

You must be very lucky to make them arranged in the same room.

$$$13^2=169,103^2=10609,130^2=16900$$$

$$$(10^k+3)^2=10^{2k}+6\times 10^k+9$$$

adding 00 to the end of number = adding 0 to the end of its square root

961 is just the same

We can generate $$$n-1$$$ numbers in this way. Add 196000000 to reach $$$n$$$.

Where is tutorial of G?

Bind your phone number may help?

Just ask some complex questions in English. Pupils won't bother you.

But I thought $$$\mathcal O(n^2)$$$ is completely different from $$$\mathcal O(n^3)$$$ solution.

My method is:$$$g[i][j]=$$$ ways to determine $$$a_1\cdots a_i$$$ and $$$a_i\neq j$$$.

Trying to solve C == Communicating with aliens

The same happened to me once too, but not in gym. I remember it was a random div2 or div3 vp.

Why so many mysterious ppl living in Antarctica

dx 1vs4

Yeah. Isn't 74 good at ds?

Got it. Thank all of you.

Plz plz give me 2 Dan I solved 4

Wow, hope this round can be friendly to me noob :)

purslane so strong

I see. Edges right under the root may not in a same color. Anyway thank you.

Yeah I use alt because 'rated' gives me more pressure.

Maybe good problems, but with trash samples.

I only shrinked $$$r$$$ of all segment instead of both of $$$l,r$$$. It got uphacked.

Hope I can reach GM after this.

qp

That's not a bug. It's feature.

White spaces and endl seem no difference to checker. 220288316

Make problems difficult enough or contain corner cases(or smth else) so that ChatGPT won't get AC.

I misunderstood it too. I wrote this

Yes,yes,but this one is stronger. A direct copy will lead to one more operation.

Hope I can solve two problems!

Bruh, my browser is always being checked. What's wrong?

Great round! Like these problems very much :3

We've found some alt ways to solve F, but they have higher time complexity.

Hi snuke

I wrote an English user editorial here.

Later, someone pointed out that it was wrong. I wrote $$$10^8$$$ but it got AC.

I've updated it and it's $$$10^{18}$$$ now.

It will be better if you can add a hack testcase. Just a cycle length $$$131072$$$ is ok.

No. Don't try to cheat.

Nice problems with small $$$N$$$ s.

Why some arc have discussions on codeforces but some don't?

When will scoring distribution come out?

edit: got it.

Nice round!

Ok. It's $$$\mathcal O(\sqrt N \log N)$$$.

Nice round! I can get a large positive delta this time.

Wrote a strange solution of B and it passed quickly. Idk whether it's right or weak data.

Scoring distribution looks friendly! I'll surely participate. GLHF!