Perhaps this is an unpopular opinion but I think we need more testers that are on the lower side of the rating spectrum. Having only red/orange testers for Div 2 contests might (and does) result in underestimation of the difficulty of the proposed problems. Blue/cyan or even green/gray form a more representative sample for the actual contestants. I understand that there should be a few highly rated and experienced testers but having only them can result in speedforces rounds for Div 2 participants.

Round 1B of the Google CodeJam contest just finished. What are your thoughts/comments on this round? I found the problems to be a bit unbalanced in difficulty which resulted in a lot of ties.

The PEG Wiki (http://wcipeg.com/wiki) is down for quite some time now although the main site (https://wcipeg.com/main) seems to be working fine. Does anybody know what happened to it? Is this something permanent? The wiki had some excellent articles which shouldn't be lost.

So I came up with this problem yesterday, which I couldn't solve. With a quick google search I found nothing relevant so I thought I could ask here for help.

The Problem

You are given a tree T with n nodes and an integer k. You are asked to find the length of longest path in T which has exactly k inversions. Here we define path inversions for a specific path P as the number of inversions in the array of the nodes visited in P, in that order. If there is no such path output  - 1.

Let's consider the above tree for example, with k = 2. The answer is 4 since the path 1 - 6 - 2 - 5 has exactly 2 inversions. Note that the path 5 - 2 - 4 also has 2 inversion however it isn't the path with the maximum length.

I am looking for solutions with complexity better than O(n²·logn)
Thank you for your time.

Sixth round of COCI 2017/2018 season will take place this Saturday at 14:00 UTC.
You can find the full schedule for this season here and register for the contest here.

Let's discuss the problems here after the contest.

Fourth round of COCI 2017/2018 season will take place this Saturday at 14:00 UTC.
You can find the full schedule for this season here and register for the contest here.

Let's discuss the problems here after the contest.

Third round of COCI 2017/2018 season will take place this Saturday at 14:00 UTC.
You can find the full schedule for this season here and register for the contest here.

Let's discuss the problems here after the contest.

Second round of COCI 2017/2018 season will take place this Saturday at 14:00 UTC.
You can find the full schedule for this season here and register for the contest here.

Let's discuss the problems here after the contest.

First round of this year's COCI will take place today at 14:00 UTC.
You can find the full schedule for this season here and register for the contest here.

Let's discuss the problems here after the contest.