### iscsi's blog

By iscsi, history, 3 years ago, ,

Hello CodeForces Community!

Chef is back again to treat you with his next delicious offering: The November Long Challenge! You are invited to showcase your coding talent and bag exciting cash prizes and goodies.

Joining me on the problem setting panel, we have:

I hope you will enjoy solving the problems. Please give your feedback on the problem set in the comments below after the contest.

Contest Details:

Time: 3rd November 2017 (1500 hrs) to 13th November 2017 (1500 hrs). (Indian Standard Time — +5:30 GMT) — Check your timezone.

Details: https://www.codechef.com/NOV17

Registration: You just need to have a CodeChef handle to participate. For all those, who are interested and do not have a CodeChef handle, are requested to register in order to participate.

Prizes: For Indians: 1st prize: INR 12000/- 2nd prize: INR 8000/- For Rest of the World: 1st prize: $400 2nd prize:$300 Top 10 global and top 20 Indian winners get 300 Laddus each, with which the winners can claim cool CodeChef goodies. Know more here: https://www.codechef.com/laddu. (For those who have not yet got their previous winning, please send an email to winners@codechef.com)

Good Luck! Hope to see you participating!

• +49

By iscsi, history, 3 years ago, ,

Hello Codeforces Community!

Wish you all a very Happy New year! Along with the celebrations we are beginning with our first contest of the year, the CodeChef January Long Challenge. The contest will go on for 10 long days. So, you have ample of time to participate, learn and code in the contest. Go ahead and check out the contest details below:

Start Time: 06th January 2017 (1500 hrs) to 16th January 2017 (1500 hrs). (Indian Standard Time — +5:30 GMT) — Check your [https://www.timeanddate.com/worldclock/fixedtime.html?msg=January+Challenge+2016&iso=20170106T15&p1=44).

Details: https://www.codechef.com/JAN17

Registration: You need to have a CodeChef handle to participate. For all those, who are interested and don’t have a CodeChef user handle are requested to register in order to participate.

Prizes:

For Global participants:

1st prize: $400 2nd prize:$300

For Indians:

1st prize: INR 12000 2nd prize: INR 8000

In addition to the above prizes. Top 10 global, Top 20 Indian, Top 5 school (Indian), Top 5 school (Global), Top 3 challenge problem solvers Indian and Global (apart from the winners) and top 5 girl coders (given that they are among top 100 in the final rank list — this will be irrespective of the region) will get CodeChef laddus, with which the winners can claim cool CodeChef goodies. Know more here: https://www.codechef.com/laddu. (For those who have not yet got their previous winning, please send an email to winners@codechef.com)

On top of all it promises to deliver on an interesting set of algorithmic problems with something for all.

Good Luck! Hope to see you participating!!

• +33

By iscsi, history, 4 years ago, ,

Hello CodeForces Community!

Happy Thanksgiving Everyone! I hope you are done with your preparations and are all set for a delectable Thanksgiving supper with your loved ones. I too would like to invite you to an early Thanksgiving celebration at CodeChef November Cook-Off. As usual it is scheduled for the second last Sunday of the month.

Joining me on the problem setting panel, we have:
- Problem setter: iscsi (Istvan Nagy)
- Contest Admin: PraveenDhinwa (Praveen Dhinwa)
- Tester and Editorialist: kevinsogo (Kevin Charles Atienza)
- Russian Translator : CherryTree (Sergey Kulik)
- Mandarin Translator: huzecong (Hu Zecong)
- Vietnamese Translator: VNOI Team

This is my first time as a short contest problem setter. The contest hero is Sebi my first child, who has three younger sister so probably he will have a hard childhood.:P I hope you will enjoy solving the problem set. Please feel free to provide your feedbacks in the comments section after the contest. You can find the rest of the details about the contest below.

Time: 20th November 2016 (2130 hrs) to 21st November 2016 (0000 hrs). (Indian Standard Time — +5:30 GMT) — Check your timezone.

Details: https://www.codechef.com/COOK76

Registration: You just need to have a CodeChef handle to participate. For all those, who are interested and do not have a CodeChef handle, are requested to register in order to participate.

Prizes: Top 10 performers in Global and Indian category will get CodeChef laddus, with which the winners can claim cool CodeChef goodies. Know more here: https://www.codechef.com/laddu. (For those who have not yet got their previous winning, please send an email to winners@codechef.com)

Good Luck! Hope to see you participating!!

• +33

By iscsi, history, 4 years ago, ,

Hello Codeforces Community!

I would like to invite you to CodeChef June Long Challenge. As always, it starts on the 1st Friday of the month and will last for 10 days. Giving you two weekends to have a go at the problems.

Start Time: 3rd June 2016 (1500 hrs) to 13th June 2016 (1500 hrs). (Indian Standard Time — +5:30 GMT) — Check your time zone.

Details: https://www.codechef.com/JUNE16

Registration: You need to have a CodeChef handle to participate. For all those, who are interested and don’t have a CodeChef user handle are requested to register in order to participate.

Prizes:

For Global participants:

1st prize: $400 2nd prize:$300

For Indians:

1st prize: INR 12000 2nd prize: INR 8000

In addition to the above prizes. Top 10 global, Top 20 Indian, Top 5 school (Indian), Top 5 school (Global), Top 3 challenge problem solvers Indian and Global (apart from the winners) and top 5 girl coders (given that they are among top 100 in the final rank list — this will be irrespective of the region) will get CodeChef laddus, with which the winners can claim cool CodeChef goodies. Know more here: https://www.codechef.com/laddu. (For those who have not yet got their previous winning, please send an email to winners@codechef.com)

On top of all it promises to deliver on an interesting set of algorithmic problems with something for all.

Good Luck! Hope to see you participating!!

• +57

By iscsi, history, 4 years ago, ,

Invitation to CodeChef February Challenge 2016!

Greetings Codeforces!!!

I hope you had a terrific start to the year and that it will continue to remain so.

I would like to invite you all to CodeChef’s February Challenge 2016: https://www.codechef.com/FEB16
Just as before the contest starts on the first Friday of February i.e. IST 1500 hrs on 05th February, 2016 and will cover two weekends ending on IST 1500 hrs 15th February, 2016. Check your time zone — http://www.timeanddate.com/worldclock/fixedtime.html?msg=CodeChef%3A+February+Challenge+2016&iso=20160205T15&p1=44.

Details: https://www.codechef.com/FEB16

Registration: Like always, the contest is open for everyone. All you need is a CodeChef account. If you do not have one, you can get it quickly here: register

Joining me on the Problem Setting panel are: maksym (Maksym Bevza), PraveenDhinwa (Praveen Dhinwa), Alex Gu, Antoniuk (Vasya Antoniuk), ma5termind (Sunny Aggarwal), Sereja (Sergey Nagin), Alex_2oo8 Alexey Zayakin
The Problems have been tested by: iscsi Istvan Nagy
The Editorials have been penned by: mogers Miguel Oliveira
The Translations for the problems came from: Antoniuk (Vasya Antoniuk) (Russian), VNOI (Vietnamese) & huzecong (Hu Zecong) (Mandarin)
And finally, the correctness of the language has been done by: RahulArora Rahul Arora

On behalf of everyone on the problem setting panel, I invite you to join the contest and enjoy the problems. There are exciting prizes to be won too.

For Rest of World participants:
1st prize: $400 2nd prize:$300

Top 10 in the same category gets cool CodeChef goodie as well.

For Indians:
1st prize: INR 12,000
2nd prize: INR 8,000

Top 20 here as well get cool CodeChef goodie as well.
In addition to all above, there are special prizes for the School Students, Top Scorers of Challenge problem, and for the Girl Coders.
All that and a crunching set of problems await you in the February Challenge 2016. I hope you will enjoy the problems as much as we have enjoyed creating them for you.

Godspeed!
See you at the contest.

• +18

By iscsi, 7 years ago, ,

Hi

I couldn't solve this problem, but I think I have some partial result what is slow that's running time is about N*sqrt(N)+Q*sqrt(N)*log(N).

The draft of my solution is: First step change from max norm (L infinity norm) to [L1 norm](http://en.wikipedia.org/wiki/Norm_(mathematics) . This means if we transorm (A,B) pairs to (C,D)=(B-A,B+A), than we can solve the problem with independently in the "x" and the "y" directions (or dimensions). We need to find the range medians of the C's. (and independantly D's.) (Of course after that we need the sum from the medians but I've just mention the position, because it is simpler, and the sum from the medians is very similiar.)

Second step I've sorted C's and calculate every 'v' value of C, and every index 'i' from 1 to n how many C's smaller than v are in the (C_1,C_(i-1)) intervall. I've try to illustrate this (this is a slower solution what I've speed up later..)

C-s: 5,1,8,3

1 3 5 8
0 0 1 1
1 1 2 2
1 1 2 3
1 2 3 4

The third column third row shows we have 2 smaller or equal value in the (C1-C3) than 5.. So if we would like to find the median of (C2-C4) than we should calculate the last row minus first row, so we've got :

1 2 2 3

So the 3 is the median :) (here switch from 1 to 2..).

In the third step I've speed up this solution (and decrease the memory usage) with square root trick and binary search (because this matrix is totally monoton I've "just" store every log N row in this matrix), so I used N*sqrt(N) memory, and the running time was N*sqrt(N)+Q*sqrt(N)*log(N).

I have some bugs so I've just past 4 test, but I don't have time at the weekend to fix this, so I've got some WA, and some TLE. So I would be very interesting how can solve this problem faster?

• +20

By iscsi, 8 years ago, ,

Hi,

I have a transition matrix ( the size ~ 50x50), and a starting probability, and I would like to calculate the first visit expectation value an special node! I can made it by simple simulation, but I had to wait about 4x10^9 iteration to stabilize the value. Is there a way to made it simpler?

• +8

By iscsi, 9 years ago, ,

Hi,

I would like to ask what is the difference 1,5 sec, 2 sec and 3 sec time limits? :)
I see some example has different time limits but I don't see when I read the problem how should I use this information? I think the memory limit is easier to calculate of course, but I can't use this time limit information.
Could you give me some idea?

thanks,

• 0

By iscsi, 9 years ago, ,
Hi,

The site is really good, I really enjoy the last competition. But I have lot of question:

1: The hacking is doesn't clear for me, how I can hacking someone else solution in the competition. I didn't see any button, I guess and hope I can't see someone else solution so I think it maybe works if someone send a "hack" then the other room player solution will be tested with this, am I right? I don't understand the timing of the hack for example is there any advantage of the sooner "hack" or late "hack"?

2: In the "problemset" menu sometimes I see the type of the problem for example dp, implemtation etc. But know I just see the 80 B, 80 A type, why? The implementation type what mean?

3: Once a time I saw problem set analysis but know I couldn't find (in the menu), where is it? :)

4: When just one division competition announced for example "Codeforces Beta Round #70 (Div. 2)" who can be a participant on this? just -1500 rating or a newbie?

5: Is there any advantage a precompiled soltion, and submit a binary than just copy paste the code and submit?

Thanks,