n0sk1ll's blog

Hello 2023
By n0sk1ll, 23 months ago, In English

Hello Codeforces!

I am pleasured to invite you to take part in Hello 2023, which will take place in Jan/03/2023 17:35 (Moscow time)!

This round consists of $$$8$$$ tasks waiting for you to solve in $$$150$$$ minutes, and will be rated for everyone!

As an author, please allow me to express my sincere thanks to:

I hope you enjoy our problems and have a wonderful $$$2023$$$!

UPD1: New score distribution is $$$500 — 750 — 1250 — 1500 — 2250 — 2250 — 2750 — 4000$$$.

UPD2: Editorial is out!

UPD3: Congratulations to the winners!

  1. Benq
  2. tourist
  3. Rewinding
  4. hitonanode
  5. jiangly_fan
  6. jiangly
  7. duality
  8. maroonrk
  9. Maksim1744
  10. DearMargaret

UPD4: Also, congratulations to the first solves of each problem!

  1. Geothermal with 187728121
  2. tourist with 187728792
  3. tourist with 187733377
  4. MEGAcrusher5000 with 187739126
  5. tourist with 187755451
  6. tourist with 187775898
  7. TLEwpdus with 187757570
  8. Rewinding with 187815792
Announcement of Hello 2023
  • Vote: I like it
  • +693
  • Vote: I do not like it

Comments Comments (216)
| Write comment?
»
23 months ago, # |
  Vote: I like it +34 Vote: I do not like it

Happy new year and we hope it will be a happy year for everyone<3

→ Reply
  • »
    »
    23 months ago, # ^ |
      Vote: I like it +8 Vote: I do not like it

    Happy New Year dear friends. May this year be the cause of the best success for all people! I wish you health and happiness!

    → Reply
  • »
    »
    23 months ago, # ^ |
      Vote: I like it -14 Vote: I do not like it

    Hi there, I'm new of codeforces, so to be consistent here I'm starting a 365 days of code streak. And this is also one of my New Year Resolutions. if you are a beginner, you can join also.

    Rules:

    1) Write a code for at least 1 problem on codeforces. You can start with the problems with minimum difficulty i.e 800. These problems take 5-10 minutes on average. Try solving one now https://codeforces.me/problemset?order=BY_RATING_ASC&tags=800-

    2) After solving the problem take the screenshot of your whole activity frame like this and send in the whatsapp group. The reason for using whatsapp is to stay connected with the group daily as most people open whatsapp at least once a day. You can mute the group also. Can be moved to a website later.

    3) Don't forget to have fun!

    register here: https://forms.gle/X3FJ4Wug33npFmYk6

    → Reply
    • »
      »
      »
      23 months ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      Why does your sign up form assume everyone has graduated high school? You know there are a ton of high schoolers (and some even younger people) who do competitive programming, don't you?

      → Reply
      • »
        »
        »
        »
        23 months ago, # ^ |
          Vote: I like it 0 Vote: I do not like it

        this post was originally for my LinkedIn circle where mostly were graduates, you can write N/A there.

        → Reply
»
23 months ago, # |
  Vote: I like it +54 Vote: I do not like it

Please don't include the number 2023 in the problems. Last contest was somewhat amazing(!)

→ Reply
  • »
    »
    23 months ago, # ^ |
      Vote: I like it +8 Vote: I do not like it

    'Please print the answer multiplied by the number 2023.' never mind...

    → Reply
»
23 months ago, # |
  Vote: I like it +20 Vote: I do not like it

I have a delta of -201 from last 5 contests, don't know how much time it will take to regain these lost points.

→ Reply
  • »
    »
    23 months ago, # ^ |
      Vote: I like it -6 Vote: I do not like it

    Maybe Hello 2023 will be enough, if you get a rank of 500-600.

    Best of luck.

    → Reply
  • »
    »
    23 months ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    around the same

    → Reply
  • »
    »
    23 months ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    Actually it depends on your performance and mentality, I've bad contest consecutively and get something like -250 (because I was just bored from contests, I didn't wanted to solve after B or something like that I was just bored), I became a spec after that while I was stuck on upper expert for months. But I was actually better than that, I earned +479 in 3 contests and became a candidate master finally.

    → Reply
»
23 months ago, # |
  Vote: I like it +1 Vote: I do not like it

Happy New Year :)

→ Reply
»
23 months ago, # |
  Vote: I like it +6 Vote: I do not like it

Good luck in the first contest in 2023!

→ Reply
»
23 months ago, # |
  Vote: I like it +55 Vote: I do not like it

As a tester, I quite enjoyed the problem set. I hope that you will enjoy the first round of 2023 and I wish you a great New Year!

→ Reply
  • »
    »
    23 months ago, # ^ |
      Vote: I like it +4 Vote: I do not like it

    Waiting for the time where tester asks for the contribution after the contest or tester criticize the problem set may be the problems those were excluded.

    → Reply
    • »
      »
      »
      23 months ago, # ^ |
        Vote: I like it +30 Vote: I do not like it

      The point of having testers is for them to criticize problems before the round so that round has good problems. Tester who says that problems are good to the coordinator, but changes after the round is a bad tester.

      And yes, I (and many other testers) did criticize one problem which was removed from the problem set and is now replaced.

      → Reply
»
23 months ago, # |
  Vote: I like it -9 Vote: I do not like it

Happy new year! Wish to get positive deltas!

→ Reply
»
23 months ago, # |
  Vote: I like it +2 Vote: I do not like it

Wishing Happy New Year and Positive Delta for everyone.

→ Reply
  • »
    »
    23 months ago, # ^ |
      Vote: I like it +7 Vote: I do not like it

    Hoping for +82 and finally achieving Cyan for the first time.

    → Reply
    • »
      »
      »
      23 months ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      go to magic section and flex on your gf

      → Reply
      • »
        »
        »
        »
        23 months ago, # ^ |
          Vote: I like it +53 Vote: I do not like it

        For that I need a gf

        → Reply
        • »
          »
          »
          »
          »
          23 months ago, # ^ |
            Vote: I like it +11 Vote: I do not like it

          fax

          → Reply
          • »
            »
            »
            »
            »
            »
            23 months ago, # ^ |
              Vote: I like it -6 Vote: I do not like it

            Or you can be like me. Downgrade your colour, show your gf, then put your colour back to the original and she will be even more proud of you.

            Spoiler:
            → Reply
»
23 months ago, # |
← Rev. 4   Vote: I like it -25 Vote: I do not like it

Happy new year everyone hope to see a year full of learning and success.

→ Reply
  • »
    »
    23 months ago, # ^ |
    ← Rev. 6   Vote: I like it -17 Vote: I do not like it

    same

    → Reply
    • »
      »
      »
      23 months ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      Because I am getting a lot of downvotes and I don't know why.

      → Reply
  • »
    »
    23 months ago, # ^ |
      Vote: I like it +58 Vote: I do not like it

    I mean, tourist isn't exactly undefeated. He has been passed a couple of times, including by Benq.

    He always comes back to the top tho

    → Reply
»
23 months ago, # |
  Vote: I like it +2 Vote: I do not like it

Happy New Year Everyone! Hoping for positive delta in Hello 2023. Upvote for good luck in 2023.

→ Reply
»
23 months ago, # |
  Vote: I like it +3 Vote: I do not like it

Interesting score distribution!

→ Reply
»
23 months ago, # |
  Vote: I like it +18 Vote: I do not like it

WOW, Serbian round, guessing some good problems :) Happy New Year for everyone!

→ Reply
»
23 months ago, # |
  Vote: I like it +11 Vote: I do not like it

It is a good opportunity to start 2023 with good contest

→ Reply
»
23 months ago, # |
  Vote: I like it +3 Vote: I do not like it

Good luck in the first contest in 2023!

→ Reply
»
23 months ago, # |
  Vote: I like it 0 Vote: I do not like it

Happy New Year

→ Reply
»
23 months ago, # |
  Vote: I like it +7 Vote: I do not like it

As a tester one day , I hope this round is a good start of 2023 and I wish you a great New Year!

→ Reply
»
23 months ago, # |
← Rev. 2   Vote: I like it +11 Vote: I do not like it

What kind of problems div1 or div2 or div3 or div4? Happy New Year

→ Reply
  • »
    »
    23 months ago, # ^ |
      Vote: I like it +5 Vote: I do not like it

    The round is combined Div 1 and Div 2. That means that problems A-F will be like div 2 A-F and problems C-H will be like div 1 A-F.

    → Reply
»
23 months ago, # |
  Vote: I like it +8 Vote: I do not like it

Happy New Year :D

→ Reply
»
23 months ago, # |
← Rev. 2   Vote: I like it -11 Vote: I do not like it

Happy New Year!

→ Reply
»
23 months ago, # |
  Vote: I like it +40 Vote: I do not like it

Hope to see Happy New Year instead of Accepted

→ Reply
»
23 months ago, # |
  Vote: I like it +13 Vote: I do not like it

Happy New Year！

→ Reply
»
23 months ago, # |
  Vote: I like it +4 Vote: I do not like it

i think problems will be short and sweet, exactly like this blog.

→ Reply
»
23 months ago, # |
  Vote: I like it -6 Vote: I do not like it

Hello guys, I'm back.

→ Reply
»
23 months ago, # |
  Vote: I like it +5 Vote: I do not like it

Happy New Year 2023

→ Reply
»
23 months ago, # |
  Vote: I like it +7 Vote: I do not like it

Happy new year 0x7e7!

→ Reply
»
23 months ago, # |
  Vote: I like it +7 Vote: I do not like it

One piece is real!!!

→ Reply
»
23 months ago, # |
  Vote: I like it +7 Vote: I do not like it

Happy 0x7e7!

→ Reply
»
23 months ago, # |
  Vote: I like it 0 Vote: I do not like it

Happy new year babyyyyyy

→ Reply
»
23 months ago, # |
  Vote: I like it +8 Vote: I do not like it

I hope this year will be a big start for many good things

→ Reply
»
23 months ago, # |
  Vote: I like it +8 Vote: I do not like it

wish every contester good luck and happy new year!

→ Reply
»
23 months ago, # |
← Rev. 2   Vote: I like it +189 Vote: I do not like it

This year will surely be lucky :

→ Reply
  • »
    »
    23 months ago, # ^ |
      Vote: I like it +67 Vote: I do not like it

    $$$\left ( 2 + 0 + 2 + 3 \right ) ^{\left ( 2 + 0 + 2 + 3 \right )} \equiv 2023 $$$ $$$mod$$$ $$$ (2 + 0 + 2 + 3)!$$$

    → Reply
»
23 months ago, # |
  Vote: I like it +9 Vote: I do not like it

Happy new year to everyone! and good luck for the first contest of 2023.

→ Reply
»
23 months ago, # |
  Vote: I like it +5 Vote: I do not like it

How difficult will be tasks? div.3?

→ Reply
  • »
    »
    23 months ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    look Score distribution, and rate of problems u solved, the most of global round is good for everyone.

    → Reply
»
23 months ago, # |
  Vote: I like it +1 Vote: I do not like it

tourist vs Benq HOW WILL WIN??

→ Reply
»
23 months ago, # |
  Vote: I like it +8 Vote: I do not like it

Hope to get to Master!

→ Reply
»
23 months ago, # |
  Vote: I like it +14 Vote: I do not like it

bestest 100% Serbian round

→ Reply
»
23 months ago, # |
  Vote: I like it +28 Vote: I do not like it

Can't wait to score first negative delta of the year.

→ Reply
»
23 months ago, # |
  Vote: I like it +10 Vote: I do not like it

Happy new Year with a new round,good luck all of you.

→ Reply
»
23 months ago, # |
  Vote: I like it +10 Vote: I do not like it

Excited for this round.

→ Reply
»
23 months ago, # |
  Vote: I like it -13 Vote: I do not like it

I got -2 because judge is not checking pretest 1 . Please help!! I got penaly because of printing unecessary things T_T

→ Reply
»
23 months ago, # |
  Vote: I like it +10 Vote: I do not like it

Coders: How many pretests do you want in Task D?

Setter: Y E S

→ Reply
»
23 months ago, # |
  Vote: I like it +38 Vote: I do not like it

Benq is mbappe

→ Reply
»
23 months ago, # |
  Vote: I like it +21 Vote: I do not like it

Benq orz. Back to Rank 1!!!!

→ Reply
»
23 months ago, # |
  Vote: I like it +14 Vote: I do not like it

seeing tourist and Benq submission times giving chills!!!!Benq orz

→ Reply
»
23 months ago, # |
  Vote: I like it 0 Vote: I do not like it

Good luck on sys tests everyone! ^_^ Hope I won't get fst.

→ Reply
»
23 months ago, # |
← Rev. 2   Vote: I like it +1 Vote: I do not like it

I think the problems setters missed a problem between B and C,there is a bit high jump in difficulty from B to C.

→ Reply
  • »
    »
    23 months ago, # ^ |
      Vote: I like it -8 Vote: I do not like it

    bro in 2nd problem I'm printing 1 and -1 sequence for even and Not possible for odd

    still showing WA why ?

    → Reply
    • »
      »
      »
      23 months ago, # ^ |
      ← Rev. 2   Vote: I like it +6 Vote: I do not like it

      Because it is possible to find answers for odd values of n.

      For example, for n = 5, we could answer [-1, 2, -1, 2, -1]

      → Reply
    • »
      »
      »
      23 months ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      it is only not possible for 3. it is possible for odd. prove that if n is odd then numbers in even positions must be equal and numbers in odd positions must be equal as well. now writing some algebra would prove u the right sequence

      → Reply
    • »
      »
      »
      23 months ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      Because it is possible for odd.

      1 -2 1 -2 1 — for any two consecutive items sum is -1 and sum of whole array is -1

      → Reply
    • »
      »
      »
      23 months ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      Only N=3 is not possible, for example in case of N=5: 1 -2 1 -2 1 is a good answer.

      → Reply
    • »
      »
      »
      23 months ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      because it is possible to create a sequence for odd n, only for number 3 you should print "NO"

      → Reply
»
23 months ago, # |
  Vote: I like it +7 Vote: I do not like it

Atmost2nforces.

→ Reply
»
23 months ago, # |
  Vote: I like it +1 Vote: I do not like it

D <<< C if you know

SPOILER ALERT

Can someone give a hint on C?

→ Reply
  • »
    »
    23 months ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    priority_queue

    → Reply
    • »
      »
      »
      23 months ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      Can't C be solved using Segment Tree with adding and RMQ, as an overkill?

      → Reply
      • »
        »
        »
        »
        23 months ago, # ^ |
        ← Rev. 4   Vote: I like it 0 Vote: I do not like it

        Sufficient and necessary condition: - For all index i < M , sum[i][M] < 0 - For i > M , sum[M+1][i] > 0

        The two subparts can be solved using priority queue.The greedy argument is to remove the smallest / largest number encountered whenever the condition is violated

        → Reply
  • »
    »
    23 months ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    Hint: priority queue

    → Reply
  • »
    »
    23 months ago, # ^ |
    ← Rev. 2   Vote: I like it 0 Vote: I do not like it

    D I got TLE with Segement Tree for some reasonmy sub

    → Reply
    • »
      »
      »
      23 months ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      Rebuilding your segment tree for every test case costs too much time.

      → Reply
      • »
        »
        »
        »
        23 months ago, # ^ |
          Vote: I like it 0 Vote: I do not like it

        It does seem so. Well that's really stupid of me. But I was in time scramble during the last 20 minutes

        → Reply
  • »
    »
    23 months ago, # ^ |
      Vote: I like it +21 Vote: I do not like it

    Actually D <<<<<<<<<<<<<<< C if you know

    big spoilers
    → Reply
  • »
    »
    23 months ago, # ^ |
      Vote: I like it +1 Vote: I do not like it

    There are two corner cases, which i found at the end of the contest. First m=1 (we don't need to check a1 <= 0). Second: (because of this wa2) the sum of prefix a1...am may be positive, neutral and negative(not only non-positive). The solution goes from transformation of inequality(destroy identical terms from left and right and you will get necessary and sufficient condition), given in the task for k>m and k<=m and considering corner cases...

    → Reply
»
23 months ago, # |
  Vote: I like it 0 Vote: I do not like it

how to solve for n = odd . problem B ?

→ Reply
  • »
    »
    23 months ago, # ^ |
    ← Rev. 2   Vote: I like it 0 Vote: I do not like it

    I have done like this. Let the entire sum be s. So A[0] + (A[1] + A[2]) + (A[3] + A[4]) ......(A[n-2] + A[n-1]) = s => A[0] + (n/2)*s = s; => A[0] = s(1-n/2)

    now A[1] = s-A[0] and similarly you can calculate for A[i]'s.

    for n=3 . its possible A[0] = 1(1-3/2) = 0.

    → Reply
  • »
    »
    23 months ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    You can list n equations. And then, the odd position number is all equal, and the even position number is all equal as well.

    Let $$$x = \lfloor \frac{n}{2} \rfloor$$$, then $$$a_{odd} = x, a_{even} = 1 - x$$$. The sum of this array is 1.

    → Reply
  • »
    »
    23 months ago, # ^ |
      Vote: I like it +5 Vote: I do not like it

    the seqance will look like this : $$$ x, y, x, y, x, ... $$$

    for $$$n=2k+1$$$ the number $$$x$$$ repeat $$$k+1$$$ times and the number $$$y$$$ will repeat $$$k$$$ times.

    the sum of the numbers are eqaul to $$$x(k+1) + yk$$$. thus we have

    $$$x(k+1)+yk=x+y\Rightarrow x(k+1)+yk-x-y=0 \Rightarrow xk+y(k-1)=0 \Rightarrow -\frac{xk}{k-1}=y$$$

    if we set $$$x$$$ as $$$k-1$$$ we can find an answer.

    → Reply
  • »
    »
    23 months ago, # ^ |
    ← Rev. 2   Vote: I like it +12 Vote: I do not like it

    Let the sequence be:

    $$$ a_1 + a_2 + a_3 + \dots + a_{n-2} + a_{n-1} + a_n $$$

    The problem states that every adjacent pair must be equal to the sum of the whole array, then

    $$$ a_1 + a_2 = a_2 + a_3 = a_3 + a_4 = \dots = a_{n-1} + a_n = \sum\limits_{i=1}^{n} a_i$$$

    So let's take a closer look to this equality

    $$$ a_1 + a_2 = a_2 + a_3 \implies a_1 = a_3$$$
    $$$ a_2 + a_3 = a_3 + a_4 \implies a_2 = a_4$$$

    Therefore you'll have something like this

    $$$ a_1 + a_2 + a_1 + a_2 + \dots + a_1 + a_2 = \sum\limits_{i=1}^{n} a_i $$$

    If $n$ is even then we fall into a trivial case where

    $$$ a_1 + a_2 = k(a_1 + a_2) $$$

    where $$$k = \frac{n}{2}$$$ because you have $$$\frac{n}{2}$$$ pairs of $$$a_1 + a_2$$$. Then you can make this equality work if $$$a_1 + a_2 = 0$$$ so you choose some $$$(a_1, -a_1)$$$

    The problem is that for an odd $$$n$$$ you have the equality like this

    $$$ a_1 + a_2 = k(a_1 + a_2) + a_1 $$$

    And that implies that $$$ a_2 = k(a_1 + a_2) $$$ so

    $$$a_2(1-k) = ka_1$$$

    For this equality to work you need to make $a_2 = k$ and $$$a_1 = 1-k$$$

    The only case where this is invalid is when $$$n=3$$$ because this would imply that $$$a_1 = 1-k = 0$$$ which violates the problem constraints

    TLDR: For odd $$$n > 3$$$ then choose $$$(1 - \lfloor\frac{n}{2}\rfloor, \lfloor\frac{n}{2}\rfloor)$$$ else choose $$$(x, -x)$$$

    → Reply
»
23 months ago, # |
  Vote: I like it 0 Vote: I do not like it

Could someone help? Why I got runtime 187832356

→ Reply
»
23 months ago, # |
  Vote: I like it +2 Vote: I do not like it

It was a nice contest, thank you. Sad, that i can't solve C... But it's ok, since this one was a quite balanced round

→ Reply
»
23 months ago, # |
  Vote: I like it +1 Vote: I do not like it

What is wrong with my last submission for C?? Can anyone help me out https://codeforces.me/contest/1779/submission/187833659

→ Reply
  • »
    »
    23 months ago, # ^ |
    ← Rev. 2   Vote: I like it +3 Vote: I do not like it

    I think you'll understand from the test

    3 3

    1 1 1

    → Reply
  • »
    »
    23 months ago, # ^ |
      Vote: I like it +1 Vote: I do not like it

    I think maybe, you made a mistake in the second for loop, where i goes from m-1 to 1 and u have put the limits as m-1 to 0.

    I made a similar mistake during the contest.

    Because whatever be the value of a1, condition a1+a2+a3...ak >= a1+a2+....am is satisfied always [a1 >= a1 + a2 + ... am leads to the condition a2 + a3 ... am <= 0].

    → Reply
»
23 months ago, # |
  Vote: I like it 0 Vote: I do not like it

Would you please debug https://codeforces.me/contest/1779/submission/187786889?

→ Reply
»
23 months ago, # |
  Vote: I like it +3 Vote: I do not like it

Someone in my room used a set instead of multiset for problem C. it is obviously wrong but i had a very hard time finding a hack test. any ideas ? i tried some numbers and i probably could get a sequence with n = 10 ish but i thought the hack test must be easier. unfortunately i didnt have enough time

→ Reply
  • »
    »
    23 months ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    Try

    1
9 1
0 -2 -2 -2 -1 -1 -1 -1 -1
    → Reply
    • »
      »
      »
      23 months ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      yeah i thought so. i dunno i guess the stress of the time got to me coz i was calculating huge numbers instead of sth easy like this

      → Reply
»
23 months ago, # |
  Vote: I like it +27 Vote: I do not like it

It was a wonderful round consisting of balanced problems with clear description. Thank you!

→ Reply
»
23 months ago, # |
  Vote: I like it +3 Vote: I do not like it

Any hint for problem E?

→ Reply
  • »
    »
    23 months ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    Plot wins as a graph. Look what that graph looks like. What happens with SCCs?

    → Reply
»
23 months ago, # |
  Vote: I like it -9 Vote: I do not like it

did um_nik tell you that B and C are garbage?

→ Reply
»
23 months ago, # |
  Vote: I like it +1 Vote: I do not like it

Great contest and amazing problems! Congrats to the author!

→ Reply
»
23 months ago, # |
  Vote: I like it 0 Vote: I do not like it

i had a negative ammount of fun doing this contest

→ Reply
»
23 months ago, # |
  Vote: I like it +1 Vote: I do not like it

Love tasks of this type, especially B

→ Reply
»
23 months ago, # |
← Rev. 2   Vote: I like it 0 Vote: I do not like it

Any idea for E? I solved by first build a tree by n-1 queries (first root=1, then for i=2 to n, do query(root,{i}), if response==1 we add an edge from root to i, else we add an edge from i to root, then let root=i), then the final root is CM. Then we try for every node i which is not CM, we do query(i,CM), if response>0 we add i and all of its ancestors into CM. But I just iterated i by natural order then I got WA on test11. Is there any better ways to choose such i to get AC?

→ Reply
»
23 months ago, # |
  Vote: I like it +8 Vote: I do not like it

Awesome Round!. The problems were very interesing.

→ Reply
»
23 months ago, # |
  Vote: I like it +16 Vote: I do not like it

First time ever I solved a segment tree problem... I wonder whether D was easier than usual BTW in which category these global round lie?(DIV1?DIV2?B/W?)

→ Reply
»
23 months ago, # |
  Vote: I like it +9 Vote: I do not like it

This is my first time solving F at div2- round and I'm really satisfied with this round. Hello 2023!

→ Reply
»
23 months ago, # |
← Rev. 2   Vote: I like it 0 Vote: I do not like it

isn't D just finding the maximum value in non matching segments of array $$$b$$$ using segment tree for all the values of $$$b$$$ (from max to min)? or am I missing something?

→ Reply
»
23 months ago, # |
  Vote: I like it 0 Vote: I do not like it

For D: https://codeforces.me/contest/1779/submission/187833014 What is the time complexity of this? Shouldn't it pass?

→ Reply
  • »
    »
    23 months ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    I am not sure but vector<vector<int>> st (k + 1, vector<int> (MAX_N)); may be slow.

    → Reply
»
23 months ago, # |
  Vote: I like it +2 Vote: I do not like it

Yesterday, I convinced my self not to think about using segment tree as the first thing that comes in to mind. I wont forgive you for making me code a segment tree after trying for an hour to find a solution not involving it :(

→ Reply
»
23 months ago, # |
  Vote: I like it +1 Vote: I do not like it

First time used PriorityQueue and SegmentTree in contest (for problem C and D).

→ Reply
»
23 months ago, # |
  Vote: I like it +4 Vote: I do not like it

benq now on first spot lets see how many days he can hold that position

→ Reply
»
23 months ago, # |
  Vote: I like it 0 Vote: I do not like it

What's the problem of this solution of D? Thanks for checking my code. 187831769

→ Reply
»
23 months ago, # |
  Vote: I like it +26 Vote: I do not like it

Getting strong pe 716 vibes from problem G

Apart from this, thank you for the contest!

→ Reply
»
23 months ago, # |
  Vote: I like it 0 Vote: I do not like it

Happy New Year Everyone and Thanks Authors for the amazing contest!! Problems were enjoyable

→ Reply
»
23 months ago, # |
  Vote: I like it +32 Vote: I do not like it

When I attempting F, I was always thinking $$$6$$$ queries is suitable for $$$2n$$$ queries problem...

→ Reply
  • »
    »
    23 months ago, # ^ |
      Vote: I like it +21 Vote: I do not like it

    Yes, $$$2n$$$ makes the problem harder lol.

    → Reply
»
23 months ago, # |
  Vote: I like it 0 Vote: I do not like it

I have an idea for problem D: sort the razors from small to large, and then think backwards. Assuming that all the hairs are on the termination condition, use the Disjoint Set to maintain the maximum operating range of a razor, and calculate whether the number of razors is enough. However, the result of my submission is WA on pretest 2. Can someone help explain it? Thanks!

my code for problem D

→ Reply
»
23 months ago, # |
  Vote: I like it 0 Vote: I do not like it

Starting two were easy and inside i was thinking yeah... new year's 1st contest is going all well.... And here comes problem C.. hmm ok approach done... all done.. But but, what is this Run Time Error on test case 2 bro. :( I got RTE like 3-4 times and at the end my brain was like, lets drop CP for few days :(

→ Reply
  • »
    »
    23 months ago, # ^ |
      Vote: I like it 0 Vote: I do not like it 
    if(arr[m-1] > 0 && m!=1)
   {
      ans++;
      sum=(0-arr[m-1]);
   }
   else if(arr[m-1] <= 0 )
      sum+=arr[m-1];

    Looking at the code block above. Before this block being executed, the value of sum is the sum of a[i] where i>=m, with some of them fliped sign. In the case of (arr[m-1] > 0 && m!=1) the code reset the value of sum to 0, but in the other case, the code executed [+=] which remained the value processed for i>=m. This will cause an error when doing pq2.top() because the value of sum is too large, and there are not enough elements in pq2.

    → Reply
»
23 months ago, # |
  Vote: I like it +3 Vote: I do not like it

i love this contest

→ Reply
»
23 months ago, # |
← Rev. 8   Vote: I like it +25 Vote: I do not like it

I'd say problems are nice. Not blaming on anyone, but hope I'm not the only one who think stronger pretests could have made this contest better with less FSTs :)

→ Reply
»
23 months ago, # |
  Vote: I like it +1 Vote: I do not like it

Happy new year~~

→ Reply
»
23 months ago, # |
  Vote: I like it +6 Vote: I do not like it

It was my first time that I solve D and only submit it for one time! :)

I love this contest, it's brilliant! And also, problems are very good too!

→ Reply
»
23 months ago, # |
  Vote: I like it +13 Vote: I do not like it

Nice problems orz n0sk1ll

→ Reply
»
23 months ago, # |
  Vote: I like it +3 Vote: I do not like it

I don't know that why B give the array a limit of 5n. And it takes me a bit time to think "why the problem gives the limit of 5n?"

→ Reply
  • »
    »
    23 months ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    btw, I even don't know why when I don't use long long at the C, it returned Runtime Error.

    → Reply
  • »
    »
    23 months ago, # ^ |
      Vote: I like it +8 Vote: I do not like it

    Perhaps the purpose of giving the limit of 5n is let the codes pass which are not implemented best. Also this can confuse someone to think "perhaps the best solution is slightly smaller than 5n", but I think this kind of strict limit could seldom appear in Problem B.

    → Reply
»
23 months ago, # |
  Vote: I like it -7 Vote: I do not like it

Thank you,FST D.

→ Reply
»
23 months ago, # |
  Vote: I like it +24 Vote: I do not like it

The problems were really interesting. Thank you authors for the contest.

→ Reply
»
23 months ago, # |
← Rev. 2   Vote: I like it +4 Vote: I do not like it

Maybe I should seriously practice div2As [Lol]. Second straight contest where I had to write a brute force program to find whats wrong with my A

→ Reply
»
23 months ago, # |
  Vote: I like it +61 Vote: I do not like it

Thanks for the contest! I liked the problems and also the loose limits for E and F (I mean $$$2n$$$), which actually made the problem harder (at least for me).

→ Reply
»
23 months ago, # |
  Vote: I like it +10 Vote: I do not like it

Nice round.I enjoy it:)

Maybe E does not seem so difficult as F while they shared the same ratings,but that doesn't matter.Anyway,Happy New Year!

→ Reply
»
23 months ago, # |
  Vote: I like it +48 Vote: I do not like it

I participated after a three-and-a-half-year absence. It was a wonderful set of problems. I'm glad this round was the one after so long.

→ Reply
  • »
    »
    23 months ago, # ^ |
      Vote: I like it +6 Vote: I do not like it

    I've participated after an exactly three-and-a-half year absense in GoodBye Round 2022. My delta was -1 and thus my graph looks funny now... but well, Today it's going to get waaaay lower hahaha.

    Just a random fact, you can continue scrolling.

    → Reply
»
23 months ago, # |
  Vote: I like it +11 Vote: I do not like it

Multiset...

→ Reply
  • »
    »
    23 months ago, # ^ |
      Vote: I like it +3 Vote: I do not like it

    Did the same mistake, but realized it when solving D, see my submissions :)

    → Reply
»
23 months ago, # |
  Vote: I like it +27 Vote: I do not like it

What a Contest in which Jiangly's Fan Beats Jiangly

→ Reply
»
23 months ago, # |
  Vote: I like it +3 Vote: I do not like it

Problems are amazing ,although not able to solve C

→ Reply
»
23 months ago, # |
  Vote: I like it +6 Vote: I do not like it

My bad. Solved D just 1 minute after the contest. Wasted a lot time with C. D was comparatively easier than C. My D submission 187838181 (No heavy algo used).

→ Reply
»
23 months ago, # |
  Vote: I like it +4 Vote: I do not like it

Pretest of C very weak

→ Reply
»
23 months ago, # |
  Vote: I like it +5 Vote: I do not like it

Could've solved D if I just had one more minute.. I think it is easier than C but I wasted too much time on C. a sad start of 2023 for me.

→ Reply
»
23 months ago, # |
  Vote: I like it 0 Vote: I do not like it

How to solve D I am getting TLE https://codeforces.me/contest/1779/submission/187829415

→ Reply
  • »
    »
    23 months ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    See my Code, just mentioned 2 comments earlier. Think it like histogram.

    → Reply
»
23 months ago, # |
← Rev. 2   Vote: I like it 0 Vote: I do not like it

In problem D, I got AC during the contest, but after the contest it shows me wrong answer in test #1. Acutally it was runtime error for test #1 and I don't know why it passed pretests. NICE ROUND :) 2023-01-03-223103

→ Reply
»
23 months ago, # |
  Vote: I like it -18 Vote: I do not like it

TOURIST ERA IS OVER

→ Reply
»
23 months ago, # |
  Vote: I like it 0 Vote: I do not like it

Can someone tell me why you don't check the first index in problem C?

→ Reply
  • »
    »
    23 months ago, # ^ |
      Vote: I like it 0 Vote: I do not like it

    because there is no sum before the first index

    → Reply
    • »
      »
      »
      23 months ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      Do you mind giving me a case where doing what I did would fail?

      → Reply
      • »
        »
        »
        »
        23 months ago, # ^ |
        ← Rev. 11   Vote: I like it 0 Vote: I do not like it

        wait

        → Reply
        • »
          »
          »
          »
          »
          23 months ago, # ^ |
            Vote: I like it 0 Vote: I do not like it

          How is the correct result 0 if the prefix sums are: -5, -1, 4. Aren't the other ones less than the last?

          → Reply
          • »
            »
            »
            »
            »
            »
            23 months ago, # ^ |
              Vote: I like it 0 Vote: I do not like it

            sorry,this is wrong

            → Reply
          • »
            »
            »
            »
            »
            »
            23 months ago, # ^ |
              Vote: I like it 0 Vote: I do not like it

            first line:1 second line:3 3 third line:5 4 3.your result is 1,but right ans is 2.

            → Reply
          • »
            »
            »
            »
            »
            »
            23 months ago, # ^ |
              Vote: I like it 0 Vote: I do not like it

            I think your make another mistake.

            → Reply
            • »
              »
              »
              »
              »
              »
              »
              23 months ago, # ^ |
                Vote: I like it 0 Vote: I do not like it

              Nah I'm getting 2. I'm talking about my 2nd to last submission during contest.

              → Reply
              • »
                »
                »
                »
                »
                »
                »
                »
                23 months ago, # ^ |
                  Vote: I like it 0 Vote: I do not like it

                I use your last submission

                → Reply
»
23 months ago, # |
  Vote: I like it 0 Vote: I do not like it

Why I don't see my rating? was it unrated for newbies?

→ Reply
»
23 months ago, # |
  Vote: I like it +2 Vote: I do not like it

Congratulations Benq for becoming the number 1 user on Cf... I wish tourist reclaims the spot in the next contest :(

→ Reply
»
23 months ago, # |
  Vote: I like it +9 Vote: I do not like it

Well Done Benq. Such performance at this young age is really mesmerizing.

→ Reply
»
23 months ago, # |
  Vote: I like it 0 Vote: I do not like it

I submitted B 3 times out of which first 2 where wrong on pretest 2. So it says — 50 points penalty on wrong submissions. I still cant figure out where those penalty points are cut. Please help Coz i am not able to figure out meaning of penalty on wrong submissions.

→ Reply
»
23 months ago, # |
  Vote: I like it +4 Vote: I do not like it

finally cyan!

→ Reply
»
23 months ago, # |
← Rev. 2   Vote: I like it +13 Vote: I do not like it

Benq orz. Back to Rank 1 <3

→ Reply
»
23 months ago, # |
  Vote: I like it +10 Vote: I do not like it

Problems are amazing and interesting!

→ Reply
»
23 months ago, # |
  Vote: I like it 0 Vote: I do not like it

I hoped to be a specialist in 2022,but I became to a specialist in the first contest of 2023.

→ Reply
»
23 months ago, # |
  Vote: I like it 0 Vote: I do not like it

could someone please explain dsu approach for problem D ??

→ Reply
»
23 months ago, # |
← Rev. 2   Vote: I like it +10 Vote: I do not like it

I was checking the approaches people used for problem D. I found it confusing and complicated I tried making a simple solution using no sorting, segment trees or any complicated data structures and just used monotone stack-

I have made a video on this let me know if you find this useful :here

→ Reply
  • »
    »
    23 months ago, # ^ |
      Vote: I like it +1 Vote: I do not like it

    It is almost the same idea as the famous histogram problem

    → Reply
    • »
      »
      »
      23 months ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      you meant infamous :P ? it has ruined the interviews of several candidates.

      → Reply
  • »
    »
    23 months ago, # ^ |
      Vote: I like it +1 Vote: I do not like it

    why is the link not working for me

    → Reply
    • »
      »
      »
      23 months ago, # ^ |
        Vote: I like it 0 Vote: I do not like it

      I think there was some issue with the link — I have changed it now could you please check again ?

      → Reply
»
23 months ago, # |
  Vote: I like it 0 Vote: I do not like it

why round is marked as unrated?

→ Reply
»
23 months ago, # |
← Rev. 2   Vote: I like it +3 Vote: I do not like it

Where is my +99 rating points?

UPD: the rating was recalculated.

→ Reply
»
23 months ago, # |
  Vote: I like it 0 Vote: I do not like it

Can anybody help with my submission of question C 187780125. The test case on which it is wrong is pretty huge :(

→ Reply
»
23 months ago, # |
  Vote: I like it 0 Vote: I do not like it

the rating was recalculated and I got additional -1 rating. Sad!

(In the other hand this make me a bit easier to get positive Delta in the next contest)

→ Reply
»
23 months ago, # |
  Vote: I like it 0 Vote: I do not like it

Your solution 187786383 for the problem 1779C significantly coincides with solutions posij118/187758161, lavijiang/187786383.Can I say this is really a coincidence? The solution of problem c is really obvious.I really didn't cheat in this contest.

→ Reply
»
23 months ago, # |
  Vote: I like it 0 Vote: I do not like it

Shouldn't I report about a guy who asks about solution during the ongoing round?

→ Reply
»
22 months ago, # |
  Vote: I like it 0 Vote: I do not like it

Ram Ram

→ Reply