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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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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https://mirror.codeforces.com/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://mirror.codeforces.com/contest/1154/problem/G (didnt solve yet)

Just solved them. These are pretty simple ones, but I like them!

1154G good problem

How about this one. Maybe it's a little simple, but I liked it.

Nice one! thanks!

This and this

Both of them were nice! Thank u!

1624G — MinOr Tree

Solved it before, but it's a great problem. Thanks!

1714F - Build a Tree and That Is It

I've solved it before, but still thanks!

1143E - Lynyrd Skynyrd

Nice one! Nice problem to practice Sparse Table!

Interesting! I did it using binary lifting — 283793892

My favourite ones: https://mirror.codeforces.com/problemset/problem/1659/E https://mirror.codeforces.com/problemset/problem/979/D

Solved them.Thanks!

General Lessoncp concepts are very limited always try to think of topics for a sec and you'll get it right by your logic (piggybacked by your intuition)

1993D - Med-imize

LessonSimple mix of binary search + DP, DP logic is also cool and simple

1992G - Ultra-Meow

LessonSimple reverse thinking for exhaustive search using basic PnC

2002D2 - DFS Checker (Hard Version)

LessonHow to use tin and tout for a generic tree and check if u is ancestor of v or not.

2002E - Cosmic Rays

LessonSimple use of stack for maintaining order (similar to sliding window maximum)

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

LessonDouble binary search n(logn)^2

2000G - Call During the Journey

Lesson:Simple Dijkstra, but from the n-1 to 0 with simple modified logic.

Also, sometimes in modified dijkstra when there could be multiple redundant entries, using a set will save you from TLE.

2008H - Sakurako's Test

LessonPre computation OR dp is necessary to not get TLE, harmonic complexity is cool. BS on range is also cool.

Almost all the problems in USACO.guide Gold with Normal and beyond rating are extremely good problems.

Auto comment: topic has been updated by incra (previous revision, new revision, compare).I can't solve the *1900+ problem/ng

Don't speak nonsense.

1973D - Cat, Fox and Maximum Array Split

ReasonI like how it's actually a data structure problem, but hidden as an interactive one. Observations are also quite nice and I had a lot of fun solving it.

This isn't a data structure problem

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

In that case, why force a data structure onto a problem when more obvious and intended sol is much much simpler?

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.

1477C - Nezzar and Nice Beatmap

1787E - The Harmonization of XOR

1965C - Folding Strip

@incra 123123123

Wonderful tree

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)

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

If it's acwing, I think u r right.

yep,acwing

I mean this problem is pretty legendary at this point: https://mirror.codeforces.com/problemset/problem/1188/B

I agree with you

https://mirror.codeforces.com/contest/2004/problem/E pretty cool game theory problem I say

CF1989E Distance to Different

Very nice counting problem.

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://mirror.codeforces.com/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

1994D

1975E

1844E

1673F

1188B

1158B

Warning: lots of constructive algorithms

Also 1355F although it's *2600