Newtech66's blog

By Newtech66, 5 months ago, In English

We'd like to thank you all for participating in the contest, and hope you enjoyed it. Hope to see you again next year!

The editorial for problem F will be added soon. It is now added.


1726A - Mainak and Array

Idea: anubhavdhar
Editorial: anubhavdhar

Hint 1
Hint 2
Solution
Implementation

1726B - Mainak and Interesting Sequence

Idea: anubhavdhar
Editorial: anubhavdhar

Hint 1
Hint 2
Solution
Implementation

1726C - Jatayu's Balanced Bracket Sequence

Idea: Newtech66
Editorial: anubhavdhar

Hint 1
Hint 2
Solution
Implementation

1726D - Edge Split

Idea: Newtech66
Editorial: Newtech66

Hint 1
Hint 2
Hint 3
Solution
Implementation

1726E - Almost Perfect

Idea: Newtech66
Editorial: Newtech66, anubhavdhar

Hint 1
Hint 2
Hint 3
Key fact
Solution 1: the easy way
Solution 2: the hard way
Implementation

1726F - Late For Work (submissions are not allowed)

Please note that it is no longer possible to submit solutions to this problem on Codeforces. You can read the details here.

Idea: little_angel
Editorial: Newtech66

Hints
Solution
Implementation

1726G - A Certain Magical Party

Idea: Newtech66
Editorial: Newtech66, anubhavdhar

Hints
Solution
Implementation

1726H - Mainak and the Bleeding Polygon

Idea: anubhavdhar
Editorial: Newtech66, anubhavdhar

Hint 1
Hint 2
Solution
Implementation

Vote for the problems here!

Feel free to vote for your opinion of each problem, and the best problem of the contest.

Vote here

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By Newtech66, 5 months ago, In English

Hello Codeforces!

Grimoire of Code, the official Competitive Programming club of IIT Kharagpur, is happy to invite everyone to take part in Codeforces Round #819 (Div. 1 + Div. 2) and Grimoire of Code Annual Contest 2022 which will take place on Sep/06/2022 17:35 (Moscow time). This round will be rated for everyone.

You will be given 8 problems and 2 hours 15 minutes to solve them.

The problems have been authored and prepared by Grimoire of Code members Anubhav anubhavdhar Dhar, Debajyoti little_angel Dasgupta, and Mainak Newtech66 Roy.


We'd like to thank all the people who made this round possible:

We hope everyone will enjoy the contest.

See you on the leaderboard!


About Grimoire of Code:

Grimoire of Code is the official Competitive Programming club of IIT Kharagpur created by and for competitive programming enthusiasts. We promote competitive programming culture in our college, and provide a forum for interested minds to discuss their thoughts and ideas. We also conduct mock coding rounds for placements and internships in Indian colleges.

You can check out our Facebook page here.

You can check out the problems from last year's Annual Contest here.


Updates

UPD1: The contest duration has been extended to 2 hours 15 minutes.

UPD2: Score distribution: $$$500-1000-1500-2000-2250-2750-3250-3500$$$

UPD3: Congratulations to the winners!

  1. Benq
  2. tourist
  3. jiangly
  4. Maksim1744
  5. kotatsugame
  6. tatyam
  7. TLEwpdus
  8. gyh20
  9. turmax
  10. Radewoosh

UPD4: Editorial (editorial for F will be added soon) It is now added.

UPD5: The contest is unrated due to problem copying. Details.

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By Newtech66, 10 months ago, In English

Hello, Codeforces!

TimeWarp101 and I are excited to invite you to Codeforces Round #782 (Div. 2) which will take place on 17.04.2022 17:35 (Московское время). This round will be rated for participants with rating lower than 2100.

Many thanks to all the people who made this round possible:

You will have 2 hours to solve 6 problems.

Scoring distribution: $$$500-750-1500-2000-2250-3000$$$

We've tried to keep the statements short and pretests strong. We hope you will enjoy the round!

See you all in the standings!

P.S. namanbansal013 will be livestreaming his solution explanations for some of the problems here. Do check out his channel too!

UPD: We are really sorry for the issues with the queue, but we hope you liked the problems anyway.

UPD: Editorial

UPD: Congratulations to the winners!

Official winners:

  1. Fire_big
  2. 20333333333
  3. _DAC_
  4. SILA_edr
  5. Nutella3001

Unofficial winners:

  1. Geothermal
  2. disorientation
  3. Koosha_Mv
  4. tute7627
  5. oleh1421

First solves:

  1. A: SSRS_ at 00:01
  2. B: SSRS_ at 00:03
  3. C: PurpleCrayon at 00:07
  4. D: noimi at 00:17
  5. E: CoderAnshu at 00:21
  6. F: rainboy at 01:06

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By Newtech66, 11 months ago, In English

Thank you everyone for your participation. Do vote under the Feedback section, and feel free to give your review of the problems in the comments.


1659A - Red Versus Blue

Idea: TimeWarp101
Editorial: TimeWarp101

Hints
Solution
Implementation (C++)
Implementation (Python)
Feedback

1659B - Bit Flipping

Idea: Newtech66
Editorial: Newtech66

Hints
Solution
Implementation (C++)
Implementation (Python)
Feedback

1659C - Line Empire

Idea: Newtech66
Editorial: Newtech66

Hints
Solution
Implementation (C++)
Feedback

1659D - Reverse Sort Sum

Idea: Newtech66
Editorial: Newtech66

Hints
Solution
Implementation (C++)
Feedback
Challenge

1659E - AND-MEX Walk

Idea: Newtech66
Editorial: TimeWarp101

Hints
Solution
Implementation (C++)
Feedback
Challenge

1659F - Tree and Permutation Game

Idea: Newtech66
Editorial: Newtech66

Bench0310 has written another proof for the solution to this problem here and here. Many thanks to him!

Hints
Solution
Implementation (C++)
Feedback

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By Newtech66, history, 2 years ago, In English

Basically the title of the post. Well, I suppose "solution->problem" is a way, but I'm not particularly good at using it. "problem->solution" is the way I prefer, but the issue is, oftentimes, I'm not skilled enough to solve the problem I just made. Nor can I tell if the problem is unsolvable (in polynomial time). How do you do it?

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By Newtech66, history, 3 years ago, In English

In newer problems on CodeForces and other sites, I usually see multi-test inputs that say something like "it is guaranteed that sum of $$$n$$$ over all testcases does not exceed XXXXX".

I am unable to figure out how to implement such a generator in Polygon. Can someone tell me how exactly I should go about this?

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By Newtech66, history, 3 years ago, In English

The problem:

Assume there are $$$n$$$ circles on the plane. The $$$i^{th}$$$ circle has an initial radius $$$r_i$$$ $$$(r_i \geq 0)$$$. We are allowed to increase or decrease the radius of the $$$i^{th}$$$ circle by $$$1$$$ unit at a cost $$$c_i$$$ $$$(c_i > 0)$$$. Let us make a graph such that each circle is a node, and there is an undirected edge between two circles $$$C_i$$$ and $$$C_j$$$ if their intersection is not empty (just to be clear, the cases are: they touch internally/externally, they intersect at two points, one lies inside the other).

Find the minimum cost to make the graph connected.

Source:

Trying to think of new and interesting problems and then creating this problem which I can't solve at all. The inspiration here was from radio stations. Every radio station has a coverage radius, and if we make the network connected, a message can travel between any two radio stations.

I have given up on this problem. I would appreciate it if someone can enlighten me on how to solve this problem or with any restrictions on it (eg. "$$$r_i=0$$$", "All $$$c_i$$$ are equal", etc).

Time complexity required:

Anything works, I haven't even been able to figure out an approach.

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By Newtech66, history, 3 years ago, In English

The problems:

Magic Portals

Surprise Birthday

Roaming

My thoughts:

Magic Portals
Surprise Birthday
Roaming

Please help me in getting a solution to each of these problems.

Note: Contest ended a long time ago so don't worry about possible cheating.

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By Newtech66, 4 years ago, In English

>bumping this post for first and last time because I never got an answer

There is an intruder in your system who wishes to steal as much information as he can. Your system can be represented as an undirected graph, with each node having an information value (IV). Now, you were terribly unprepared for this. Your only option is to delete nodes. You have time enough to delete at most 2 nodes. Luckily, the algorithm of the intruder has a flaw. It cannot visit a previously visited node. It steals the information of whatever node it visits. Assuming that the algorithm always tries to maximize the IV it can get, give the maximum possible IV you can save.

Note: Formally the algorithm seeks the path of maximum weight. The sum of the weights of the unvisited nodes is what you have saved. The weights of the deleted nodes are unavailable to both you and the algorithm. When a node is deleted, all paths connected to it are also removed.

A variant: Now you are given that the algorithm starts the path with a given vertex that you cannot delete.

There are no constraints, I want the best solution. Please notify any corrections or flaws in the problem statement. It is guaranteed that the constraints allow a solution.

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