Whistle's blog

By Whistle, history, 8 days ago, In English,

How to find the Kth parent using sparse table technique

Link of the Video

This video is targeted towards newer members in competitive programming; I explained everything about sparse table technique starting from the base information.
It only require a simple knowledge in: DFS algorithm, Binary system, and tree structure.

I have already discussed in my previous blog about the type of the problems to make in my Youtube channel, and I have decided to pick up some interested problems and make tutorials of them.
I was going to explain the solution of Whistle's New Car in this video, but it will make the video so long (witch seems boring).
that why I decided to explain its solution, which based on sparse table technique, in another video.

This is my first video, and my first experience in making video tutorials; so please guys leave any comments or advice about the video.

Please don't forget to subscribe the channel and thanks in advance for watching

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By Whistle, history, 5 weeks ago, In English,

As a way to give back to the amazing community, I will make a Youtube channel
explaining algorithm techniques and Codeforces problems solutions.
It will be targated towards newer members who are not very experienced in competitive programming yet.
The problems will be at level Div2 D-E up to Div1 D.

I want to know which method do you prefer ?
1- pick up some old problems that I find interesting and explain the solution and the techniques that I used.
2- pick up a problem from the last contest on Codeforces and explain the solution and the techniques in that problem.

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By Whistle, history, 5 months ago, In English,

BTW guys, it's a fun blog and no offense for problem setters and I really appreciate their efforts

well, first of all you have to know that you have to find 5 problems
now you can follow the hard way and invent interesting problems by your own or you can follow my tips
for Div2 A:
it's so easy just put a list of strings and assign a value for each of them and put a random question like find the sum of values of the strings that contain "Bombi-bombi" , "Dombi-dombi" or "Tombi-tombi" as a substring
no matter what the question is but try to make the problem required to copy things from the statement as much as it possible, so users can't solve it under 2 minutes

for Div2 B:
problem of leap years are very suitable for this level
put any random question of leap years so users should spend time reading about it in Wikipedia
and don't forget to make the pretest weak, so participants can waste their time on hacking and then only few number of users will solve all the problems(that's gonna make your round looks hard)

for Div2 C:
pick a random problem from any online judge and make a slight change on it
it's gonna be easy for you since this kind of problems are easy to change and easy to understand
so if the original problem ask for the minimum value make it for the maximum value or maybe you can make it for both of them (clever huh ? )

for Div2 D/E:
don't be afraid, even if you're a Newbie and you can't even understand the solution of that problems
it's alright buddy but you have to be careful
because all you have to do is to pick a problem from an online judge which hide submissions of solved problems
change the statement (not the idea or what is required) and you can use the solution and the code of one of the users
for more efficiency try to pick it not that famous, so users can't find it that easily

Finally:
no matter if you used the first way or the second, remember CF will pay you and will accept your problems magnanimously and you will get upvotes on your announcement
Note it's a very important step : after the round say sorry for CF community and tell them that you didn't notice that they're copied problems

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By Whistle, history, 6 months ago, In English,

so ? in the last 3 months we hadn't got any "good" round
always there are technical problems, copied problems or whatever
now CF is getting larger and larger and the number of active users is hitting the wall of 10 thousand or maybe more
that means we want a stronger severe and better services
so till when?
are these issues temporary or they're because of a weak server?
how long we should wait to enjoy our rounds ?
CF really is my favorite site for CP but I started to get boring from this situation

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By Whistle, history, 9 months ago, In English,

Yesterday was the final competition of WRO (World Robot Olympiad)
the results should be posted soon here
Anyway, this year, especially in my country, WRO has received alot of medial hype and I find it's now more famous than IOI.
I think that because robots are more desirable and it's looked that it's too difficult to build them.
I haven't participated before in any Robot Competition, so I don't know much about it
if anyone of you has participated before in WRO
please tell me about the situation there and how much is it difficult to success there compared to the IOI ?
and which one of them do you think is bigger deal and received more attention ?

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By Whistle, history, 12 months ago, In English,

Hello everyone!

today most IOI teams will arrive to their countries
hope you have a great trip and hope you had a great days in Russia
so could you please tell us about your experience
what is your result, what was your strategy for the contest and did it work?
and tell us about the organization there
were there a good food, a good treatment and an interesting activities ?

please attach some photos if you have.
here is the closing ceremony, looks like it was wonderful

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By Whistle, history, 12 months ago, In English,

Today most IOI teams will be arrived to Russia but not Turkish Team, not Ukrainian team
every year at least two teams don't participate at IOI because of a political reasons
in the next year IOI 2017 will take place in Iran, Iran doesn't like both USA and Israel
so probable USA team and Israel team will not participate in IOI 2017
The equation is if your country has a good relationship will The host country then you're lucky you will participate if not, Umm we are sorry we don't have any place for you.
this is not a silly game, Turkish Team and Ukrainian team have International Grandmaster, International master, 3 masters and 4 Candidate Master.
do you know what does that mean , it means that this people have worked hard all the nights preparing for IOI
you don't have the right to prevent them from participating and kill their dreams because of your silly political reasons. now this shit must be end
for all IOI teams, please appeal every single person in charge of IOI , talk about that to everyone you see
I don't know, do anything you can do, because this must be end.
when any country given the right to host IOI, it should pledges to accept every participant from any country. any give him a Visa.
anyway, good luck for IOI teams
hope not to see such things anymore.

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By Whistle, history, 13 months ago, In English,

According to Alexa CF's rank is 13,475 by now after it was about 25k in the last year
interesting fact that the largest percentage of visitors is from India 37.5%
and only 19.9% from Russia

more details

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By Whistle, history, 13 months ago, In English,

contest standing

and here is the test case

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By Whistle, history, 15 months ago, In English,

A little while ago there were a blog and I wrote a long comment To explain something
then when I clicked on post bottom , simply " you don't have the access to write a comment "
then I realized that the blog has been deleted ,that's really bothers me
now the question , Why is it allowed to delete the whole blog not just edit it (like in comments) ?

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By Whistle, history, 15 months ago, In English,

last month I have participated in ACM competition in my country , I heard many funny team names
so what is your team name and what is the story behind it ?
addition : what is the most funny team name you had ever heard ?

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By Whistle, history, 15 months ago, In English,

there are N items and a budget of D dollars
each item has a stock S (you can buy at most S of that item) A, B , and value X
the cost for k of that item is (A + (k-1)* B)
what is the maximum value can be attained given this budget ??
1 <= N <=2000
1<= D <= 5000
1<= X,S <= 10^7
0<= B <= A <= D

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By Whistle, history, 16 months ago, In English,

APIO 2016 (Asia-Pacific Informatics Olympiad) will take place in 7-9 may 2016 hosted by Republic of Korea .
official site . competition rules .

Practice session will start at 3 May and end in 5 May .
wish good luck for all participants .
UPD : practice session has been started , Link.
UPD2 : contest has been started and it will end at 8 May 11 GMT. UPD3 : open contest day has been ended

Problems : problem 1 , problem 2, problem 3
UPD4 :Official results
congratulation for all medals winners
first place : yokozuna57 and namonakiaccount
second place : yutaka1999

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By Whistle, history, 16 months ago, In English,

I heard many top-guys say that when their solutions get WA for reasons they can't find, they usually generate tests and compare the output on a bruteforce solution with the output on their fast solution. Do you have a script to do that, or each time you generate test and try it on both solution? Could you elaborate on when and how you do it?

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By Whistle, history, 22 months ago, In English,

Why do you do competitive programming?

I know most of you does it for fun, but when it comes to practicing 5+ hours a day, I don’t think it should be just for fun (or you’d be wasting your time).

What do you think competitive programming would do for you? Get you to a college? A dream job?

One month ago (and until now) I’m practicing for minimum 3 hours a day, and this really affected my school grades. I don’t have much time for studying anymore. However I’m doing it to improve my skills in order to be able to achieve a medal in the IOI, which would boost my admission to one of the top colleges.

I was wondering what do you think, and why do you do it?

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