Codeforces Round #218 (Div. 2): Tutorial The tutorial has been prepared by [user:Fefer_Ivan,2013-12-08] and [user:NALP,2013-12-08]. ### [problem:371A] For array to be periodic, elements $1, 1 + k, 1 + 2*k, …$ must be equal. Also, elements $2, 2 + k, 2 + 2*k, …$ must be equal. And so on up to $k$. So each element of the array is a part of exactly one group. And there are $k$ groups total. Each such group is independent. Let’s consider some group of elements, that contain $a$ ones and $b$ twos. All elements in this group must be equal. So we either change all ones to twos or all twos to ones. First option will require $a$ changing operations and second one — $b$ changing operations. For the optimal solution, you should select the operation with smaller number of changing operations required. ### [problem:371B] It is easy to see that the fox can do three type of operations: divide by 2, divide by 3 and divide by 5. Let’s write both given numbers in form $a=x\cdot2^{a_{2}}\cdot3^{a_{3}}\cdot5^{a_{5}}$, $b=y...

Full text and comments »

Round #173 — Editorial Hi, Here's the editorial. Please note that not all the codes presented below belong to me. (It's a combination of codes from our problemsetters and testers) -- And I borrowed [user:AKGMA]'s account since I wasn't able to link to my own submissions somehow! Note: It seems that the Codeforces mark-up is not functioning. To see a submission go to: http://www.codeforces.com/contest/282/submission/submission-number #### A: **Bit++** Just use a simple loop. (Take a look at the Python code) GNU C++: [submission:3314442], [submission:3314464] GNU C: [submission:3314471] Python: [submission:3314475] #### B: **Painting Eggs** This one can be solved by a greedy algorithm. Start from the 1st egg and each time give the egg to A if and only if giving it to A doesn't make the difference > 500, otherwise give it to G. To prove the correctness, one can use induction. The base case is trivial. Suppose that we've assigned the first $n-1$ eggs such that the total money given to ...

Full text and comments »

North Macedonia TST 2025 - a week to remember Last week (02/12 — 07/12) the North Macedonia TST for EJOI, EGOI and IOI took place in the Univerzitet Sv. Kiril i Metódij, where we were hosted by professor Biljana Angelova. The teams were selected based on contestants results on four different contests. There also were several classes on different common competitive programming topics, like FFT, Li Chao Tree, and 3D Convex Hull presented by [user:ReaLNero,2024-12-07] and [user:forelax,2024-12-07]. The contest were IOI-like, each lasting around 12 hours, with no breaks, in order to prepare contestants to adverse testing conditions. (Just kidding, they were standard 5 hours contests) Day 0 ------------------ On the first day, we didn't have any tests, since everyone was just arriving. However, we had to move to another hotel, since a particular group of people were making too much noise and got us banned from the hotel. (They were watching Sausage Party 2 and laughing too much with it. Highly recommend this awesome movie bt...

Full text and comments »

Tutorial Codeforces Round #430 (Div. 2) [problem:842A]) Let's denote the potion's amount of experience as $exp$ and its cost as $cost$. We want to know if there is a potion such that $exp$ and $cost$ meet the following condition: $\frac{exp}{cost} = k$. To do this, we can iterate on $cost$ from $x$ to $y$ and check that $exp = k \cdot cost$ is not less than $l$ and not greater than $r$. https://ideone.com/a8syda [problem:842B]) To understand whether some piece of sausage intersects with pizza, we can check if their borders intersect. And to check this, since their borders are circles, we are interested in their radii and the distance between their centers. To check if a piece of sausage is inside the crust, we firstly check that it is inside the pizza $(\sqrt{x^2 + y^2} ) + cr \le r$), and secondly check that it is completely outside the central part of the pizza $(\sqrt{x^2 + y^2} \ge r - d + cr$). https://ideone.com/Jd66XL [problem:842C]) It's easy to see that if the number written on some vertex $...

Full text and comments »

ACM-ICPC 2011 Finals: Beginning <p>The train number nine from Saratov to Moscow was a pleasant surprise. Every compartment in our wagon had a small TV, outlets, and each passenger could use a personal safe with a code lock. Of course, we didn't turn the TV on and didn't use the safes. Imagine how ironic it would be if we put there, say, a passport and forgot the code number.</p> <center> <img src="http://assets.codeforces.com/photos/finals-2011/p_IMG_4116.JPG" style="width:500px"><br><small>Note that there's not only a TV, but also also outlets behind Nickolay.</small> </center> <p> In Moscow we had a little snack in some seedy railway eatery (in fact, Kolya and Artem went to Mcdonalds) and got on an express to the Domodedovo Airport. The fun lasted 40 minutes and cost 12 USD rubles each. Russian Railways have a good business![cut]</p> <p> We met Roman Alekseenkov (<span class="Apple-style-span" style="border-collapse: collapse; font-family: verdana, arial, sans-serif; font-size: 13px; "><a href="http:/...

Full text and comments »

HSE studies Hello team end DONT WORRY))))))))xDDD thx for helping in [user:0icq,2024-01-19] about a can going studi in HSE VERY BIG TY :D (recspect) and super thaks to [user:maxan,2024-01-19] becouse thats very nice pupil in mipt technologies university (call). Maxan is very respectful nice mipt student LOL For starting i can want to say that it was so hardy to me to being student HSE (cool). It was so compressive for my psycho heal because i was thought a big and my brain is so dead and i wanted to going go for a walk with my friends [user:islam_ahmed,2024-01-19] (nice to meet you) and [user:ivan_09090,2024-01-19] (BIG bRO) but I WAS SO STREIGHT AND NEED TO shoes. ok LETS GO to review HSE letsplay xDD its my friend his brain so smart [user:0icq,2024-01-19]  thats a his social network page in HSE internet https://www.hse.ru/staff/bigshishiga like and subscribe him plese is so close well then about HSE is so comfortable place in the ...

Full text and comments »

WA in Sausage Maximization Hello all, I am trying to solve the problem [Sausage Maximization](http://codeforces.me/contest/282/problem/E). I am solving it using the approach mentioned in the editorial for the question. I am getting Wrong answer on Test 33 on the following submission. [Submission](http://codeforces.me/contest/282/submission/17916236) I have tried a lot of test cases, but I am unable to find any error in the implementation. It would be really helpful, if someone could point out some error in the implementation,

Full text and comments »