Suppose I have 4 rows of numbers(The row size is n)

a1, a2 , a3 ,... an

b1, b2 , b3 , ....,bn

c1, c2, c3,... cn

d1, d2, d3,... ,dn

I need to find number of ways to select numbers from each row exactly once such that a < b < c < d.

For example if rows are

2,3,4,5

3,4,5,6,

4,5,6,7,

5,6,7,8

Then one possible way is (2,4,6,8) ; select 2 from first row, 4 from second and so on.

Other than brute force , what could be another way of solving this problem? [Note: brute force cant be used if length of rows is large]

I don't understand why my code is showing runtime error on test 2. I tried but could not find the problem . Please help. The code. Problem C of educational codeforces round 98. The problem.

I write C++ code in Dev-C++ and test it locally before submitting the final solution. Which IDE can I use for Kotlin? I want to take part in 12 November contest. TIA :)

Well straight to the point. I can't afford online programs on DSA (expensive for me). I generally Google all my doubts, but sometimes I don't get my doubts clarified. Although whenever I have posted something on codeforces, most of the time my doubts are cleared.

I feel it would have been much better if I can contact some specialist, expert aur candidate master (preferably on Messenger)with whom I could have shared my ideas on problems.

Currently my rating is 1276. (Had to mention this because I have not mentioned pupil above).

I would be thankful if someone is willing to help me . Thanks in advance :).

Recently I had watched a video where Gennady tourist Korotkevich said that upsolving doesn't help because that question will not be repeated in future contests. So, is upsolving a waste of time? Pls help.

This is outside CP. Just asking because I am interested in Russian music:) Please don't mind.

I want to know the names of very popular Russian singers in 2020. Since I joined this website, I started learning Russian language (apart from CP) , because I was very much fascinated by the language. Recently I have heard Russian music and I enjoyed it:). Don't remember the name of the singers although :( .

I don't understand , am I not eligible to ask questions because I am not a specialist or expert? Few minutes ago I asked for help regarding a topic. Just asked for some resources which help me learn that stuff. I asked this because I feel that Watching some random videos on that topic won't help.

However I am receiving downvotes for asking question? I really can't get this . Was there something wrong in the question? It is not that I have not tried understanding that topic. I have watched EDU section and read CSES cp handbook . I tried a lot but still can't get the idea that's why I asked it on codeforces. Random downvoting should end. It is really frustrating.

Hello Codeforces!

(I don't want my friends to see me that's why I created this account).

Till now I am able to solve basic cp problems on binary search, two pointer,constructive algorithms, implementation and sometimes greedy problems on codeforces. By basic I mean upto tag 1300. However when it comes to tags like DP, tree, graph (which requires knowledge of recursion) I falter. I thought that the EDU section on codeforces will come up with recursion topic but I guess it has started with DSU after string suffix and binary search. The EDU section has helped me a lot in solving problems.

I also read few chapters of CSES Competitive Programming handbook by Antti Laaksonen. (suggested by pllk) It is a great book but it does not cover recursion in detail. (Chapter 5 deals with recursion little bit)

Please suggest some resources so that I can learn this topic. And hopefully can overcome my fear. :)

Thanks in advance! :)