incra's blog

Leave your favourite problems rating between [1900,2400]!
By incra, history, 3 months ago, In English

I can't find many nice problems, so please drop some problems even if it's naive!

Updata: Just found out that *2100 was not hard enough :)

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3 months ago, # |
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https://codeforces.net/contest/1360/problem/G

tbh it is a good problem but i didnt feel like it was this hard maybe cuz i solved alot of matrix problems but aye it was nice for me :)

this also might be good https://codeforces.net/contest/1154/problem/G (didnt solve yet)

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3 months ago, # |
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How about this one. Maybe it's a little simple, but I liked it.

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3 months ago, # |
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This and this

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    3 months ago, # ^ |
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    Both of them were nice! Thank u!

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3 months ago, # |
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1624G — MinOr Tree

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    3 months ago, # ^ |
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    Solved it before, but it's a great problem. Thanks!

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3 months ago, # |
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1714F - Build a Tree and That Is It

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    3 months ago, # ^ |
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    I've solved it before, but still thanks!

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3 months ago, # |
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1143E - Lynyrd Skynyrd

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3 months ago, # |
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My favourite ones: https://codeforces.net/problemset/problem/1659/E https://codeforces.net/problemset/problem/979/D

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3 months ago, # |
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General Lesson

1993D - Med-imize

Lesson

1992G - Ultra-Meow

Lesson

2002D2 - DFS Checker (Hard Version)

Lesson

2002E - Cosmic Rays

Lesson

Find Kth smallest pair distance in an array: Leetcode HARD (but simple bs actually)

Lesson

2000G - Call During the Journey

Lesson:

2008H - Sakurako's Test

Lesson
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    3 months ago, # ^ |
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    Almost all the problems in USACO.guide Gold with Normal and beyond rating are extremely good problems.

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3 months ago, # |
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Auto comment: topic has been updated by incra (previous revision, new revision, compare).

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3 months ago, # |
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I can't solve the *1900+ problem/ng

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3 months ago, # |
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3 months ago, # |
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1973D - Cat, Fox and Maximum Array Split

Reason
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    3 months ago, # ^ |
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    This isn't a data structure problem

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      3 months ago, # ^ |
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      Does the problem become any easier if you know the array? (it actually does due to some hack solutions, but it's not trivial)

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        3 months ago, # ^ |
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        In that case, why force a data structure onto a problem when more obvious and intended sol is much much simpler?

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          3 months ago, # ^ |
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          Co-author of the mentioned problem here. Originally the problem was supposed to be solved knowing the whole array, but over the time, we figured out that it impossible to cut-off unintended bruteforces while letting all implementations of the model solutions pass. Making a black-box RMQ+binary search data structure and hiding the original array was the best solution I could think of.

          So in a way, the problem is still a data-structure problem, as it requires the contestant to figure out an efficient way to use a given a data structure.

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3 months ago, # |
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1477C - Nezzar and Nice Beatmap

1787E - The Harmonization of XOR

1965C - Folding Strip

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3 months ago, # |
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@incra 123123123

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3 months ago, # |
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Wonderful tree

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3 months ago, # |
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1560F2 - Nearest Beautiful Number (hard version)

1154G - Minimum Possible LCM

1367F1 - Flying Sort (Easy Version)

1367F2 - Flying Sort (Hard Version)

1156E - Special Segments of Permutation

1560F2 - Nearest Beautiful Number (hard version)

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3 months ago, # |
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Wait,I think I have seen you on the acring web.Is that the right name?no for sure

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3 months ago, # |
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I mean this problem is pretty legendary at this point: https://codeforces.net/problemset/problem/1188/B

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3 months ago, # |
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https://codeforces.net/contest/2004/problem/E pretty cool game theory problem I say

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CF1989E Distance to Different

Very nice counting problem.

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3 months ago, # |
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A problem authored by a friend of mine and I was the first tester to solve this and did it with an unintended solution

https://codeforces.net/contest/1735/problem/E

The funniest thing is it was supposed to be a Div2C, but after testing it became Div2E and got a rating of 2400

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3 months ago, # |
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1994D

1975E

1844E

1673F

1188B

1158B

Warning: lots of constructive algorithms

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