Looks like there was not much news regarding this, but the 60 year old bound of the Gomory-Hu tree was broken in a recent paper: arXiv.

Semifinal 1 is live at https://go.twitch.tv/topcoder_official.

Good luck to all. Special good luck for scott_wu, who just won $10,000 from another contest 9 hours before (for reference it is OpenBracket, but that's off topic for now)

Congrats to Yuta yutaka1999 for winning this year IMO!

Edit: name. Never write on mobile phone again, sorry.

Welcome to another Codeforces Round!

Please note that the time of round #191 was changed. Contest will start at Thursday 12:30 UTC.

My name is Linh (ll931110). I'm from Vietnam, and I'm glad to present to you my first Codeforces round. It is for Div 2 only; however, I welcome participants from Div. 1 to participate and enjoy challenging problems. I hope this would be a pleasant gift for those who are going to IOI 2013 (and participants from World Finals), which will take place in just a couple of days.

This round is prepared by me and fchirica (from Romania). Also, I would like to thank the Codeforces team who puts efforts on making Codeforces and Polygon possible.

Happy solving!

UPD1: The score of problems in this round will be dynamic. The problems will be sorted in increasing difficulty order, at least in our perspective.

UPD2: The contest is over! Congratulations for everybody, especially for those who solved E. You proved to be smarter than I am (your solutions were totally unexpected to us). Thank Gerald, Aksenov239 and Delinur for helping us on preparing the round!

Div. 2 winners:

1. SillyHook02

2. Tsukiko

3. Quit_Quickly

4. Zhengxu

5. sevenzplus

Those are five people who nail all problems!

Unofficial winners:

1. Kissshot

2. R_R_

3. xchernoff

4. wakaka

5. phtniit

The editorial will be completed soon after revising and adding possible alternative solutions. You are welcome to post your answers in comments.

Thank you and see you in the next round!

UPD3: Editorial is now available. Remind that it is not the final version, as we are writing possible alternative solutions for problems. Stay tuned!

UPD4: Editorial is now completed.

Today, I've found an interesting book which discusses and gives detailed analysis for several problems in Algorithmic Engagement see this link. However, as you can see, it's just a preview. I wonder if it's possible to buy or download the full book?

I hope anyone (especially Polish coders) could help me on this :)

Link to problem statement (problem D)

For short, in this problem, one is provided the minimal cut matrix T (T(u,v) equals to the minimum cut so that u and v are disconnected), and one needs to find a graph G that satisfies T.

I have solved this problem using the observation: if the solution exists, it must be some sort of spanning trees (it also seems to be the author's solution). However, I have no way to prove my observation. Any hint?

Currently I'm writing an article for my school in algorithm. I pick the topic about Manhattan distance, thus I need your help of finding problems in this topic. Any sources (past Codeforcces, ACMs, OIs, SRM, etc.) would be accepted, and I'd appreciate if you could give some hints for some difficult problems.

Thank you for your help!

Recently, in a couple of contests, I have been unable to view others' codes after locking my problems. The screen just turned blank after I opened any codes. So, which version of Flash should be installed to fix this issue? I'm using Ubuntu 11.10. Thanks for your help!