Reminder: in case of any technical issues, you can use the lightweight website m1.codeforces.com, m2.codeforces.com, m3.codeforces.com. ×

### giorgosgiapis's blog

By giorgosgiapis, history, 9 months ago, ,

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.

• +17

By giorgosgiapis, history, 13 months ago, ,

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)

• +8

By giorgosgiapis, history, 20 months ago, ,

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.

• +28

By giorgosgiapis, 22 months ago, ,

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.

• +31

By giorgosgiapis, 23 months ago, ,

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.

• +29

By giorgosgiapis, 23 months ago, ,

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.

• +41

By giorgosgiapis, 2 years ago, ,

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.