Requesting Editorial/Explanation for WKPLAN

As far as I know, the editorial for WKPLAN is not available. I was very interested in the problem but could not solve it. The only 3 people to solve it during the contest were @mcfx1, @rns5 and @yfzcsc so I ask everyone but especially those 3 to provide an explanation.

Here was my progress at the time which I had also written here:

I was able to show that given sum can be written as \displaystyle \sum_{n=1}^N \Big(f*h(n)\Big)\Big(n^p\Big)

Where * represents Dirichlet Convolution and h(n) counts the number of ways to chose m numbers such that their gcd is 1 and their lcm is n.

h can be written in terms of other common functions related to Dirichlet Convolution as h = \mu * \mu * d^m. Their meaning can be found in the wiki I linked.

And the whole sum written in terms of common functions is \displaystyle \sum_{n=1}^N (f*\mu *\mu *d^m)\cdot(Id_p)(n)\ where \cdot represents pointwise multiplication.


20 character lower limit :unamused:

@vijju123 Any possibility of setter notes??

Remind me once I am over this frickin chicken pox :frowning:


I was thinking why weren’t you much active on Codechef/Discuss since a loooong time…now I came to know :frowning: Hope you get well very soon :slight_smile:

Get the setter notes well soon.
No rush since it’s not in your control.

I saw that you posted recently. Hope you are fine now. Really desperate for those setter notes.

1 Like

Thanks for reminder. Looking into it. :slight_smile:

1 Like

Any updates, @vijju123 ?

Yup, a sad one. There is no setter’s solution of it in Codechef Database - which happens when setter directly PMs the problem idea to contest admin instead of submitting via the form. Perhaps the contest admin that time (I think @mgch ) might be able to help, but that seems unlikely :cry:

1 Like