atcoder_official's blog

AtCoder Beginner Contest 421 Announcement
By atcoder_official, history, 13 months ago, In English

We will hold AtCoder Beginner Contest 421.

We are looking forward to your participation!

  • Vote: I like it
  • -372
  • Vote: I do not like it

Comments Comments (138)
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13 months ago, hide # |
 
Vote: I like it +6 Vote: I do not like it

let's go!

good luck to everyone giving it

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13 months ago, hide # |
 
Vote: I like it +5 Vote: I do not like it

Orz

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13 months ago, hide # |
 
Vote: I like it +3 Vote: I do not like it

On the last conteset, I only have 300 scores. I'm very mad.

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13 months ago, hide # |
 
Vote: I like it +3 Vote: I do not like it

Good luck to everyone!

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13 months ago, hide # |
 
Vote: I like it 0 Vote: I do not like it

Hope AC E vOvOv

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13 months ago, hide # |
 
Vote: I like it 0 Vote: I do not like it

qpzc

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13 months ago, hide # |
 
Vote: I like it +1 Vote: I do not like it

oh, I can't access atcoder.(sad I got only 300points qwq.

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13 months ago, hide # |
 
Vote: I like it +34 Vote: I do not like it

SUPER RUBBISH ROUND.

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13 months ago, hide # |
 
Vote: I like it 0 Vote: I do not like it

why is it so hard???

i got 1575 last round and 300 this round...

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    13 months ago, hide # ^ |
     
    Vote: I like it 0 Vote: I do not like it

    What are these numbers about?

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    13 months ago, hide # ^ |
     
    Vote: I like it 0 Vote: I do not like it

    Me too... I thought it was so easy but only got AC on ABC. Last time I got AC on ABCD.

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      13 months ago, hide # ^ |
       
      Vote: I like it 0 Vote: I do not like it

      I think B needs to be solved using a string. Don't be discouraged, maybe this competition is just a fluke. Next time you participate in ABC, you will find... The problems in ABC are a shit.

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        13 months ago, hide # ^ |
         
        Vote: I like it 0 Vote: I do not like it

        Well... perhaps he's meaning he only got ACcepted on problem A & B & C this time, instead of only worked out A and C and didn't figure out B in the Atcoder Beginner Contest (ABC).

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13 months ago, hide # |
 
Vote: I like it +28 Vote: I do not like it

DOWNVOTE!SUPER RUBBISH ROUND.(

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13 months ago, hide # |
 
Vote: I like it +35 Vote: I do not like it

Worst ABC I have seen.

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13 months ago, hide # |
 
Vote: I like it +32 Vote: I do not like it

Sorry, but D was one of the most annoying, tedious case work problem I've ever encountered on AtCoder. I genuinely hated this round.

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13 months ago, hide # |
 
Vote: I like it +1 Vote: I do not like it

very bad round

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13 months ago, hide # |
 
Vote: I like it 0 Vote: I do not like it

how to solve C

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    13 months ago, hide # ^ |
    ← Rev. 2  
    Vote: I like it +6 Vote: I do not like it

    try to keep any letter 'A' or 'B' in even and odd positions and find the distance between the current and actual position and add it to res. Return which arrangement return min cost.

    • If we have string AABBBA
    • Let place B in odd positions and final result be BABABA here the cost is 2+1=3
    • Let place B in even positions and final result be ABABAB here the cost is 1+1=2
    • so min cost is 2
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13 months ago, hide # |
 
Vote: I like it 0 Vote: I do not like it

Is there any optimal approach other than LinkedList for question F.Erase between X and Y

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13 months ago, hide # |
 
Vote: I like it +1 Vote: I do not like it

why is f easier than d and e

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13 months ago, hide # |
 
Vote: I like it -37 Vote: I do not like it

great round

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13 months ago, hide # |
 
Vote: I like it +32 Vote: I do not like it

problems were a mess—either too boring or way too complicated. The difficulty doesn’t make sense, and some problems seem designed just to waste time

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13 months ago, hide # |
← Rev. 2  
Vote: I like it +19 Vote: I do not like it

F<<<<<D

upd: i can somehow understand that D is much easier than E in thinking of their solutions, but how the hell is a linkedlist F? in terms of thinking F≈D and in terms of coding F<<<<<<<<<D

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13 months ago, hide # |
 
Vote: I like it +1 Vote: I do not like it

RUBBISH ROUND. 300 ppl E 600 ppl F 130 ppl G

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13 months ago, hide # |
 
Vote: I like it 0 Vote: I do not like it

Wasted so much time on E(still don't know how to solve it) makes me have no time to solve G.

trash D, G is great.

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13 months ago, hide # |
 
Vote: I like it 0 Vote: I do not like it

我过了ABCDEF,G来不及看

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13 months ago, hide # |
 
Vote: I like it +1 Vote: I do not like it

Worst ABC.

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13 months ago, hide # |
 
Vote: I like it +12 Vote: I do not like it

D is sh*t!

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13 months ago, hide # |
 
Vote: I like it +1 Vote: I do not like it

very bad round,downvote!!!

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13 months ago, hide # |
 
Vote: I like it -6 Vote: I do not like it

A shit contest.

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13 months ago, hide # |
← Rev. 3  
Vote: I like it 0 Vote: I do not like it

hp

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13 months ago, hide # |
 
Vote: I like it +3 Vote: I do not like it

F is a lot easier than D and E. D was too impl heavy + boring and hence had no motivation to solve it. Really feeling the quantity over quality...

For F, an offline way to check if X comes before Y: Create the digraph (type 1 x->i) and check toposort order.

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13 months ago, hide # |
← Rev. 5  
Vote: I like it +1 Vote: I do not like it

D is a bit boring with heavy implementation. I have no motivation to solve the problems :(

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13 months ago, hide # |
 
Vote: I like it +1 Vote: I do not like it

D是什么东西 D is 【"Harmonious" words】

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13 months ago, hide # |
 
Vote: I like it +16 Vote: I do not like it

F is much easier than E and D. Swapping E and F makes a lot of sense.

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13 months ago, hide # |
 
Vote: I like it +14 Vote: I do not like it

swap(D, F) plz... D is tooooooooo boring.

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13 months ago, hide # |
 
Vote: I like it +1 Vote: I do not like it

what a super rubbish round.

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13 months ago, hide # |
 
Vote: I like it +3 Vote: I do not like it

awful contest.

Hope can replace D with F.

I am so mad when I have WA*10 in D everytime.

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13 months ago, hide # |
 
Vote: I like it +11 Vote: I do not like it

Atcoder Implementation Contest

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13 months ago, hide # |
 
Vote: I like it +9 Vote: I do not like it

史

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    12 months ago, hide # ^ |
    ← Rev. 3  
    Vote: I like it -16 Vote: I do not like it

    Wow so respectless. You posted a Chinese means "shit " in English

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      12 months ago, hide # ^ |
      ← Rev. 2  
      Vote: I like it -8 Vote: I do not like it

      I have always held the view that a contest with standards strictly inferior to those my classmates and I could randomly organize is not worth wasting 10k users' time for 100 minutes. In this situation, it is permissible to insult the contest.

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13 months ago, hide # |
 
Vote: I like it +7 Vote: I do not like it

this contest is meaningless at all

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13 months ago, hide # |
 
Vote: I like it +6 Vote: I do not like it

Why is the next ABC on Sunday at 12:10 (Beijing time)

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13 months ago, hide # |
 
Vote: I like it +1 Vote: I do not like it

SUPER RUBBISH ROUND

i got 2575 last round and 600 this round...

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13 months ago, hide # |
 
Vote: I like it 0 Vote: I do not like it

Bullshit contest.

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13 months ago, hide # |
 
Vote: I like it +1 Vote: I do not like it

I am new to AtCoder, how much time does it take tentatively for the ratings to update?

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13 months ago, hide # |
← Rev. 2  
Vote: I like it +9 Vote: I do not like it

No comment. Plz downvote this ??? contest.

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13 months ago, hide # |
 
Vote: I like it +9 Vote: I do not like it

Although I got a good result, I still have to say that this contest was really bad, especially the D problem.

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13 months ago, hide # |
 
Vote: I like it +9 Vote: I do not like it

It's hard to believe that scores of 650 and 2025 came from the same contestant. I think it was a bad round.

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13 months ago, hide # |
 
Vote: I like it +3 Vote: I do not like it

For D, you should get the right idea, then it is not so complex

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13 months ago, hide # |
 
Vote: I like it +3 Vote: I do not like it

Problem D is too boring! I hate it!

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13 months ago, hide # |
 
Vote: I like it +8 Vote: I do not like it

我们对爱并不陌生 你知道规则，我也知道 我所想的是一个完整的承诺 你不会从其他人那里得到这个的 我只是想告诉你我的感受 必须让你明白 永远不会放弃，永远不会让你失望 永远不会跑来跑去抛弃你 永远不会让你哭泣，永远不会说再见 永远不会说谎伤害你

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13 months ago, hide # |
 
Vote: I like it +23 Vote: I do not like it

垃圾ABC412!!!

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    12 months ago, hide # ^ |
    ← Rev. 4  
    Vote: I like it +21 Vote: I do not like it

    Edit: previously I put Chinese comment before the English translation, and I'm sorry. Now I deleted Chinese content.

    Why don't you think about your own behavior when your account is banned by the anti-cheat system? You escalate it to personal attacks. Do you think you are supreme?

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13 months ago, hide # |
← Rev. 2  
Vote: I like it +49 Vote: I do not like it

image

recall.cpp
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    13 months ago, hide # ^ |
     
    Vote: I like it +13 Vote: I do not like it

    前节写“洒江郊” 的茅草无法收回，除此以外，还有落在平地上可以收回的茅草，但却被“南村群童”抱跑了。“欺我老无力”五字宜着眼， 如果诗人不是“老无力”，而是年当壮健有气力， 自然不会受这样的欺侮。“忍能对面为盗贼”，意思是，群童竟然忍心在他 的眼前做盗贼。但其实，这不过是表现了诗人因“老无力” 而受欺侮的愤懑心情而已，决不是真的给“群童”加上“盗贼”的罪 名，要告到官府里去办罪。所以，“唇焦口燥呼不得”，也就无可奈何了。用诗人杜甫的《又呈吴郎》一诗中的话说，这正是 “不为困穷宁有此”，诗人如果不是十分困穷，就不会对大 风刮走茅草那么心急如焚；“群童”如果不是因为他十分困穷，也不 会冒着狂风抱走那些并不值钱的茅草。这一切，都是结尾 的伏线。“安得广厦千万间，大庇天下寒士俱欢颜”的博大胸襟和 崇高愿望，正是从“四海困穷”的现实基础上产生出来的。

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13 months ago, hide # |
 
Vote: I like it +8 Vote: I do not like it

Atcoder Beginner Contest is getting better and better(doge

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13 months ago, hide # |
 
Vote: I like it +3 Vote: I do not like it

The worst ABC I have ever attended.

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13 months ago, hide # |
 
Vote: I like it +10 Vote: I do not like it

I think D was difficult(wording atleast) compared to F. In F you just have to use a linked List nothing else. (T_T)

Spent too much time in problem D and multiple wrong attempts due to silly mistake.(T_T T_T)

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13 months ago, hide # |
 
Vote: I like it +5 Vote: I do not like it

long long died in D(AC23,WA1),no time in E,maybe FG<DE???

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13 months ago, hide # |
 
Vote: I like it +1 Vote: I do not like it

ABC will be infamous

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13 months ago, hide # |
 
Vote: I like it +1 Vote: I do not like it

The contest is bad. I don't like this contest. Hello , Fwb !

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13 months ago, hide # |
 
Vote: I like it +8 Vote: I do not like it

You don't need to show that you have problems in your brain by making CP problems.

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13 months ago, hide # |
 
Vote: I like it +28 Vote: I do not like it
Spoiler
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13 months ago, hide # |
 
Vote: I like it 0 Vote: I do not like it

AT什么神经AI检测，搞了20分钟了还是进不去

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13 months ago, hide # |
 
Vote: I like it +1 Vote: I do not like it

This contest is really SHIT!!! Speailly, Problem D & E are pretty sick.

ABC is more worse.

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13 months ago, hide # |
← Rev. 2  
Vote: I like it -18 Vote: I do not like it

It seems that many people think this round is not good. Maybe I'll receive many downvotes, but i still consider this round a good round.

You may think this round is too hard as a "Beginner Contest". Yes, that's fact. However, this round is very meaningful and educational to me. For example:

  • D is a problem requiring careful simulation/implementation, and you can train your coding abilities from it.
  • F is a problem with multiple solutions, linked list or balanced tree. The first solution requireds more thinking, and the second solution will train your ds skills. Personally i think this problem is good.
  • G is a classical mcmf, that's surely educational

At least that's better than previous totally speed round and rounds with too large gap.

Indeed, this round also has shortages, like E easier than F, etc, but abc as an educational contest, this round's meaning is more than its shortage.

Also i think saying something like problem xxx is shit is lack of basic respect. If you have different opinions please comment below

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13 months ago, hide # |
 
Vote: I like it +4 Vote: I do not like it

D is full of IF. That's terrible.

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13 months ago, hide # |
 
Vote: I like it +3 Vote: I do not like it

Solved D using ternary search

Submission

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13 months ago, hide # |
 
Vote: I like it +4 Vote: I do not like it

A good contest for Mr.Fwbeast.

But not a good contest for people.

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13 months ago, hide # |
← Rev. 3  
Vote: I like it +9 Vote: I do not like it

Everybody say D is boring ， but if you use Relative motion，the code can be very short.

Please don't complain that the question is disgusting, in fact, there should be an easier way.

this is our teachers' code.

https://atcoder.jp/contests/abc421/submissions/68930507

it's just about 60 lines mainly. if you use Relative motion,it can shorter than 50 line.

Without logic, OI will no longer be an art, and so will life.

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13 months ago, hide # |
 
Vote: I like it 0 Vote: I do not like it

a boring contest

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13 months ago, hide # |
 
Vote: I like it 0 Vote: I do not like it

Though my rating increased after this round, I think D and E are the worst problem I have ever met in AtCoder.

I got rank 4700 before I ACed D and became rank 120 after that.

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13 months ago, hide # |
 
Vote: I like it 0 Vote: I do not like it

This abc is so cute!

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13 months ago, hide # |
 
Vote: I like it 0 Vote: I do not like it

Fwb Round #421

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13 months ago, hide # |
 
Vote: I like it 0 Vote: I do not like it

D is so boring. It shouldn't be appeared in ABC.

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13 months ago, hide # |
 
Vote: I like it 0 Vote: I do not like it

For problem D, I think considering from the two dimension vector might help simplify the implementation. For instance, assuming that two points have positions (x1, y1) and (x2, y2), and current operations have (dx1, dy1) and (dx2, dy2). Then, we should find some positive k satisfying x1+k*dx1=x2+k*dx2, and y1+k*dy1=y2+k*dy2.

Problem E is once again abc's favorite [expectation and maximum] pattern. We should maintain two states, how many steps are left, and what numbers we have kept.

Problem F can be solved based on linkedlist, and in fact I usually use array to simulate the linkedlist. For the query of the second type, we only need to find out whether x is in front of y, or vice versa. We can solve this part by using that classic trick, [one chase after the other one]. We start simultaneously from x and y, and move forward until we meet y or x, and then stop. This method can guarantee a linear complexity O(N).

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13 months ago, hide # |
 
Vote: I like it +1 Vote: I do not like it

i think codes of D and E may be too long for beginners

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13 months ago, hide # |
 
Vote: I like it 0 Vote: I do not like it

samples are too weak

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13 months ago, hide # |
 
Vote: I like it +6 Vote: I do not like it

Could someone please help with problem E? It’s a really nice problem.

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13 months ago, hide # |
 
Vote: I like it 0 Vote: I do not like it

Pure shit of implementation

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