Hi Codeforces, I'm working on building a social network platform for competitive programming, all its users should have the same interest in CP and there will be many exclusive features & contents the CPers can enjoy,

For example:

1- 1vs1 coding challenge matching (like chess game matching), the user can choose if this gonna be public so anyone can view the challenge, common friends only, or only some community members.

2- team matching, the user can choose if it is ICPC team, so the recommendations will recommend only the users who are in the same organization, or casual team matching.

3- Meeting request matching, user can request to have a meeting with someone to explain or teach him something, the algorithm will match his request to users and users can accept or not, these meetings can be paid too (like uber matching maybe).

4- during live rounds, users can see a live scoreboard for the users in their connection, or in some community.

5- in users newsfeed they can view tutorials for the problems they couldn't solve (WA/TLE/..etc verdict) during live rounds,

6- users can create communities and each community can have its own sub-community (for example: community_x has 3 sub-communites like newcomers, seniors, leaders).

7- rating change celebrations

• the motivation behind this is to make the competitive programming community more closer and more enjoyable
• Will you be interested to join or not? Please, feel free to share your feedback.

Hello guys I'm trying to be good at counting using combinatorics.

Can anyone recommend some tutorials/problems for me ... Thanks in advance and RAMADAN KAREEM

Hello every one ,wish you are doing great .... can any one explain how does this code doesn't got TLE ? https://codeforces.net/contest/246/submission/79394388

My idea is:

1-I'm storing all nodes in subtree of u at depth x using dfs time.

2- In every query first I check if I've encountered a query asking about the same nodes then I print answer as I save the ans of every query else then I iterate over all strings at depth d[i] + x at subtree of u and find number of distinct strings using set.

thanks in advance