### pllk's blog

By pllk, history, 2 weeks ago,

Today we have released a new version of the CSES Problem Set:

https://cses.fi/problemset/

CSES Problem Set is a collection of algorithmic programming problems that can be used to practice competitive programming. We have now added 100 new problems, and the total number of problems is 300. There are both easy and difficult new problems, and some of them cover advanced topics, such as treaps, suffix structures, and FFT.

In 2020, there were more than one million submissions to CSES, which is a new record. Thank you for your submissions and new test cases through hacking!

Our ultimate goal is to create a problem set of 1000 problems, so you can expect many new problems also in the future. If you have ideas on how to improve the problem set, you can discuss them here.

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 » 2 weeks ago, # |   +10 Thank you for the problems
 » 2 weeks ago, # |   +34 Great. Make it like one stop Platform where any beginner can blindly follow.
 » 2 weeks ago, # |   +140 Sample explanations please.
•  » » 2 weeks ago, # ^ |   +74 Yes, we are working on it
•  » » » 2 weeks ago, # ^ |   -13 Thank you!
•  » » 19 hours ago, # ^ | ← Rev. 2 →   -8 hidden comment
 » 2 weeks ago, # |   -60 Please add tutorial option in the problem statement page if possible.
 » 2 weeks ago, # |   +9 https://cses.fi/problemset/task/2413/ Counting TowersI am missing a proper defintion on how to count distinct towers. Is a rotation or a reflection another tower?
•  » » 2 weeks ago, # ^ |   +10 Thanks, now the problem statement should be easier to understand.
 » 2 weeks ago, # |   0 yanire Yoav Noam13 almogwald inbarin Back to the grind?
 » 2 weeks ago, # |   0 Thanks a lot !
 » 2 weeks ago, # |   +8 Why does trying to hack Digit Queries give internal error?
•  » » 2 weeks ago, # ^ |   +8 Thanks, now it should be fixed
 » 2 weeks ago, # |   +13 How to sort problems by difficulty level?
»
2 weeks ago, # |
Rev. 3   +72

For anyone else, like me, curious for a list of just the new 100 problems to look through:

by category
 » 2 weeks ago, # |   -27 Thanks for this but i have a suggestion :Do not increase numbers , but focus on quality . Create a problemset which cover all possible topics of Competitive Programming with minimum number of problems. Else there will be no difference a online judge and this set . You can add other practice problem to a different section .
 » 2 weeks ago, # |   +1 Nice good sir.
 » 2 weeks ago, # |   +24 Thanks for doing this, I really appreciate your book and the problemset!Couple of questions: Is there any way to hide problem "tags" like DP, Graphs, etc? The only thing that stopped me from solving CSES is that you know if the problem will be DP or Graphs or Math in advance, thus making it less interesting. Why 1000 problems? It feels great to solve everything, and this will be hard to do with 1000 problems, just from the time standpoint. 200 was perfect for this, 300 is not bad. I think it's possible to cover most essential topics/techniques, and still keep the problemset size small.
•  » » 13 days ago, # ^ | ← Rev. 2 →   +25 To make it more interesting, solve only Additional Problems. All others are just "implement classical algorithm". So even if you hide topics, they become obvious when you read problems.
•  » » 13 days ago, # ^ |   +15 If you've started at the right time, after each expansion you only have to solve a 100 new problems :P
•  » » 13 days ago, # ^ |   +31 The idea is that the "tutorial" problems are divided into sections and then there are more difficult problems in the last section without hints. With 300 problems the problem set is already quite comprehensive, but there are still many good educational problems that are missing. I agree with your point that it may take really long to solve them all in the future.
 » 2 weeks ago, # |   0 please add some decent questions of constructive algorithms to practice
•  » » 2 weeks ago, # ^ |   0 Yeah, Constructive Algorithms are the most widely asked topic in these days contests. Add some good level Problems on Constructive Algorithms !!
 » 2 weeks ago, # |   +4 best problemset for beginners and intermediates. thankyou!
 » 13 days ago, # |   +4 I think it would be great if there are discuss section like leetcode.Some problems are quite hard for beginners like me to figure out the solution all by myself.
 » 13 days ago, # |   +4 You are doing a great Job. Thank you!
 » 13 days ago, # |   0 The problems are really good. One suggestion: why not change the time limit for non-Cpp programs? I try submitting the solution in Java and it TLEs. Just converting it to cpp gets accepted.
 » 13 days ago, # |   +105 I always dreamt of being 1st on the CSES leaderboard, but I never imagined being 2nd simultaneously!
•  » » 11 days ago, # ^ |   +33 "There are only two hard things in computer science: cache invalidation and naming things."
 » 13 days ago, # |   0 orz pllk
 » 13 days ago, # |   0 Nice initiative.....
 » 12 days ago, # | ← Rev. 2 →   0 Firstly, thank you for the helpful initiative!I had a small clarification in this regard. The original post mentions the addition of problems based on some advanced concepts like treaps, suffix structures, and FFT. I just wanted to enquire as to if the book contains an explanation for these topics as well.If not, can this please be done ?Once again, thank you!
•  » » 11 days ago, # ^ |   +10 At the moment no, someday it will contain. Before that there are other sources that can be used to learn the topics.
•  » » » 11 days ago, # ^ |   -6 Okay, thank you!
 » 12 days ago, # |   0 Official editorials of the problems may be a good idea.
 » 12 days ago, # |   +25 Our ultimate goal is to create a problem set of 1000 problems
 » 8 days ago, # |   0 Thank you for the amazing problem set!I think it is the best website for someone who want to learn some new algorithm
 » 7 days ago, # |   0 Can you please add the sample explanations for the sample test case? I am finding some problems a little difficult to understand like Prefix sum queries.
 » 28 hours ago, # | ← Rev. 2 →   -14 Suggestion: add hacking leaderboards or some other way of crediting hackers.Perhaps add next to a testcase the name of the person who added it? There are a few possibilities.
•  » » 27 hours ago, # ^ |   +6 People will abuse it. Please take a look at educational round hacks.
 » 13 hours ago, # |   0 Can anyone please help me out with the Counting Tilings problem?? I haven't been able to find any recurrence relation.Any hint??
•  » » 10 hours ago, # ^ |   +3 HintI think it's bitmask dp, so $dp[i][mask]$ would be the answer for a $n \times i$ grid such that its $i$th column has positions covered at $mask$.