Errichto's blog

By Errichto, 3 weeks ago,

Target audience: newbies and pupils (rating up to 1400).
Group link: https://codeforces.com/group/yg7WhsFsAp/contests (hit "join" on the right).

Hi. Enjoy a series of 8 problem lists for beginners. The example topics are strings, arrays, math, and binary search. You are allowed to discuss anything with others, or just look up solutions online. There are also 3 exams, each recommended for a 2-hour individual virtual participation. Use the displayed order, e.g. take exam 1 after day 3. It all should take you 2 weeks of intense bootcamp-like work (or a few months if you take your time).

The problems were originally used two years ago in a Saudi Arabia camp. It's a mix of around 70 existing CF problems and 30 new original problems, mainly prepared by kostka, with some help from me and mustafabar. I asked them for permission to publish everything.

I will put hints to some problems in this blog (or in the group? not sure). Expect a few videos and/or streams for beginners too. You should also read two first chapters of Competitive Programmer's Handbook.

UPD: On Sunday evening I'm making a stream with explanations to a few hard problems: P8, P11, P18, P30, P31, P33. You can try it with hints first:

P08. Cashier
P11. Queens attack!
P18. Mountain peaks
P30. Temporarily unavailable
P31. Shuffle Hashing
P31. Shuffle Hashing, hint 2
P33. Thanos Sort

• +245

 » 3 weeks ago, # |   +19 Thanks a lot :D I'll try to solve all of them in the upcoming days
 » 3 weeks ago, # |   +7 It is really usefull
 » 3 weeks ago, # | ← Rev. 2 →   +1 Can those not in the rating range specified above not submit ? Edit : Just checked, they can
•  » » 3 weeks ago, # ^ |   +25 You are allowed, but the problems should be easy and boring for you.
 » 3 weeks ago, # |   0 Awesome!!!!
 » 3 weeks ago, # |   -8 you mind putting some more tough questions in there .
•  » » 3 weeks ago, # ^ |   +11 These are problems from a camp two years ago. The participants were beginners just after learning basic C++.
•  » » » 3 weeks ago, # ^ |   0 ohk i got it
 » 3 weeks ago, # |   0 This will help me a lot!
 » 3 weeks ago, # |   0 thanks a lot
 » 3 weeks ago, # |   -28 Can you prepare another one for 1400 to 1600? I will be very helpful! And thanks for preparing this one. I will submit these problems.
 » 3 weeks ago, # |   0 Awesome
 » 3 weeks ago, # |   0 There is no problem numbered P17 in day 2
•  » » 3 weeks ago, # ^ | ← Rev. 2 →   +16 Oh, you are right. I see now that we removed it back then because it required an algorithm that participants didn't know yet. It was 1041B - Buying a TV Set.I've renumerated problems.
 » 2 weeks ago, # |   0 Thanks for this bootcamp Errichto , Can we expect more such bootcamps with a certain level up anytime :) .
 » 2 weeks ago, # |   +14 Reminds me of whenever I say I should start over competitive programming from the beginning since I am not good at the basics.
 » 2 weeks ago, # |   0 Hey!! Thanks a lot, it will surely help a lot.
 » 2 weeks ago, # |   0 Great , it will help us a lot.
 » 2 weeks ago, # |   0 I have just finished the basics of java and solved 100 URI basic problems and some hackerrank easy problems. need to read the first two chapters of "Competitive Programmer's Handbook". it will take some time. I will try it.I have a question. if someone wants to try it after 3/4 months will these problems will be there?
•  » » 2 weeks ago, # ^ |   +12 Sure. I don't plan to ever hide these problems.
•  » » » 2 weeks ago, # ^ |   0 Hi It says "You are not allowed to take part in the group contest" if i click register.
•  » » » » 2 weeks ago, # ^ |   0 You have to join the group first. See the page's right side and you'll see "Join Group" in this (https://codeforces.com/group/yg7WhsFsAp/contests) link.
•  » » » » » 2 weeks ago, # ^ |   0 thank you
•  » » » 13 days ago, # ^ |   0 thank you so much
 » 2 weeks ago, # |   0 Thanks a lot. Please arrange more Bootcamp or practice sessions like this for newbies.
 » 2 weeks ago, # |   0 Really awesome. I hope I enjoy and learn.I am really grateful for it.
 » 2 weeks ago, # |   0 When I try to register it says "you are not allowed to enter", I am new to this platform. how to register for this.
•  » » 2 weeks ago, # ^ |   0 Actually it says " You are not allowed to take part in the group contest "
•  » » » 2 weeks ago, # ^ |   +12 Come on. Read the top of the blog. Or just scroll up by a few comments.
•  » » » 2 weeks ago, # ^ | ← Rev. 2 →   0 First you gotta join the group using this -> https://codeforces.com/group/yg7WhsFsAp/contests. Then you can register!
 » 2 weeks ago, # |   0 where will i find the editorial of practice problem of day 1
 » 2 weeks ago, # |   0 Any hints/tips on how to solve P48 The line problem
•  » » 12 days ago, # ^ | ← Rev. 2 →   0 The hint is in the original question already. It gave an unnecessary/redundant information which could have been omitted.
 » 2 weeks ago, # |   0 hey there i am trying to solve Day 2 P13 lost rectangle problem for almost a day now and ain't able to come up with a possible solution nor could find anything on the interent to help, coud anyone please help my with some possible idea . I would be realy helpful.https://codeforces.com/group/yg7WhsFsAp/contest/355493/problem/P13
•  » » 2 weeks ago, # ^ |   0 Hint 1Prime is a big hint in itself. Hint 2The Area A is made by two integer (as given) sides. So, using this fact you can determine that for any integer to be the height or breadth of rectangle, It should evenly divide the A. Hint 3Just find all the prime factors of A, and then say for any factor p, we can treat it as 1 of the side of rectangle. Therefore, the other side is A/p. Now, you have both the side. Find the Perimeter using the same idea for all the factors of A, and print minimum one to the result.
•  » » » 13 days ago, # ^ |   0 You use one word incorrectly: Spoiler"prime" -> "divisor"If the area is 100, possible shorter side lengths are 1, 2, 4, 5, 10. These are divisors, not primes.
•  » » » » 13 days ago, # ^ |   0 Oh yes, I meant the same thing just got confused with right terminology.Thanks for the correction.
•  » » » » 11 days ago, # ^ |   0 I cant solve it... :(
 » 13 days ago, # |   0 This bootcamp will last for how many days?
•  » » 13 days ago, # ^ |   0 2 weeks from the day of start of each section
•  » » » 13 days ago, # ^ |   0 And what about topics? Only strings, arrays, math, and binary search?
•  » » » » 11 days ago, # ^ |   0 Yes most of them are observation based as far as what i have seen so far
 » 13 days ago, # |   0 How much time would you recommend to try to solve one problem by yourself, before moving to editorials (stuck on p48)
 » 11 days ago, # |   0 How can I get all the solution of this boot camp problems ?? I would be very helpful for me... Thank you
 » 10 days ago, # |   0 I don't know if it is right to discuss it here, but it is related to a question in this bootcamp. do let me know if I am not supposed to ask or post anything here. I am new to this platform.In a particular problem if I use. for(size_t i=0; i * i <= n ; i++) //I get TLE where n is upto 10e12. for(size_t i =0; i<=sqrt(n) ; i++) //The answer gets accepted is there any difference(in performance)? if yes then an explanation will be helpful.
•  » » 10 days ago, # ^ |   +11 i * i overflows. You need to use (long long) i * i.
 » 5 days ago, # |   0 good joob errichto thanks bro for questions
 » 5 days ago, # |   0 can any one help me slove primes question 1(lost rectangle)
•  » » 5 days ago, # ^ | ← Rev. 2 →   0 SpoilerA= l*b; safe to assume one of sides 1<=l<=10^6. so other side will be A/l. l has to divide A. Solutionll a; cin >> a; // 2(l+b) = p , l.b = a, 2*(l+ a/l)=p ll p=1e18,pmin=1e18; for(int l=1e6;l>=1; l--) { if(a%l==0) pmin = min(2*(l+ a/l),pmin); } cout <
•  » » » 4 days ago, # ^ |   0 thanks alot man
•  » » » » 4 hours ago, # ^ |   0 How do u take minimum of something in C++? any idea?