Codeforces Beta Round #17 Tutorial <a href="http://mirror.codeforces.com/blog/entry/447">Contest discussion</a><br><b><br>Problem A. Noldbach problem<br><br></b>To solve this problem you were to find prime numbers in range $[2..N]$. The constraints were pretty small, so you could do that in any way - using the Sieve of Eratosthenes or simply looping over all possible divisors of a number.<br>Take every pair of neighboring prime numbers and check if their sum increased by $1$ is a prime number too. Count the number of these pairs, compare it to $K$ and output the result.<br><br><b>Problem B. Hierarchy</b><br>[cut]<br>Note that if employee, except one, has exactly one supervisor, then our hierarchy will be tree-like for sure.<br>For each employee consider all applications in which he appears as a subordinate. If for more than one employee there are no such applications at all, it's obvious that $-1$ is the answer. In other case, for each employee find such an application with minimal cost and add these costs to get the answer.<br...

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Codeforces Beta #27 - Tutorial <p> <size =="" 18=""><strong>A. <a href="http://mirror.codeforces.com/contest/27/problem/A">Next Test</a></strong></size><br> We will create an array of boolean used[1..3001] ans fill it with "false" values. For each of n given number, we will assign corresponding used value to "true". After that, the index of first element of used with "false" value is the answer to the problem.<br><br> <size =="" 18=""><strong>B. <a href="http://mirror.codeforces.com/contest/27/problem/B">Tournament</a></strong></size><br> To solve this problem first of all we should find such numbers A and B that occur in the input data not (n - 1) times, but (n - 2). We can notice, that winner-loser relation in this problem is transitive. This means that if X wins against Y and Y wins against Z, than X wins against Z. So to find out who is harsher A or B, let's look for such C, that the results of the match A with C and B with C are distinct. If such C exists, than the one, who wins against C should be printed first. I...

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Codeforces Beta Round #73 <p></p><div style="background-color: transparent; margin-top: 0px; margin-left: 0px; margin-bottom: 0px; margin-right: 0px; "><span id="internal-source-marker_0.25316758337430656" style="background-color: transparent; vertical-align: baseline; ">Hello everybody and welcome to the first summer round - Codeforces Beta Round #73.</span></div><div style="background-color: transparent; margin-top: 0px; margin-left: 0px; margin-bottom: 0px; margin-right: 0px; "><span id="internal-source-marker_0.25316758337430656" style="background-color: transparent; vertical-align: baseline; "><br></span></div><p></p><div>Today we are the authors of round: <a href="http://mirror.codeforces.com/profile/kuniavski" title="Полковник kuniavski" class="rated-user user-red" style="font-family: arial; text-decoration: none !important; font-weight: bold; color: rgb(0, 0, 204); ">kuniavski</a>&nbsp;(Pavel Kunyavskiy) and<span class="Apple-style-span" style="font-family: Arial; font-size: 15px; white-space: pre-wrap; "> </sp...

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Codeforces Beta Round #27 (Codeforces format, Див. 2) <div><div>We want to congratulate you with a happy new school year with this contest. We wish you excellent marks, easy exams and many Accepted in the contests. Let this year bring you many new and interesting knowledge!</div><div><br></div><div>Artem Rakhov and Codeforces&nbsp;team&nbsp;</div><div><br></div><div>P. S. Note that the round will be held on the <a href="http://mirror.codeforces.com/blog/entry/456">Codeforces Format Rules</a>. Read the rules before&nbsp;the competition. Good luck!</div></div><div><br></div><div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; font-family: verdana, arial, sans-serif; font-size: 12px; line-height: 20px; "><b>UPD:&nbsp;</b></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; font-family: verdana, arial, sans-serif; font-si...

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[Beta] Harwest — Git wrap your submissions this Christmas! Hi beautiful people of Codeforces! Hope you'd all be doing fine and keeping safe. I'd like to start by mentioning that it's been a while since I graduated from university ever since which I haven't completely been able to indulge myself in competitive coding in the same way I did back in my university. But I sure haven't forgotten those days. I had some time off from work recently and decided to spend my time giving back to the community from where I have learned so much. In the thought of so, I've built this tool which I like to call [`Harwest`](https://github.com/nileshsah/harwest-tool) (a play on the word Harvest since the package name wasn't available anymore :'D) It's one of those tools which I would have loved to have during the time when I used to practice rigorously on this platform. **Harwest** allows you to manage all the submissions that you've made on Codeforces, or on other OJs (WIP) into one single Git repository which you can then push to your personal Github...

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Codeforces Round #983 (Div. 2) ### Hello Codeforces! $\newline$ <spoiler summary="From AkiLotus"> > "<span style="color: red">K</span>aleidoscopic, this place still is. How long have I been away...?" Hi. Akik<span style="color: red">a</span>ze a.k.a. AkiLotus here. Four years have passed, lo<span style="color: red">n</span>g enou<span style="color: red">g</span>h huh? I h<span style="color: red">o</span>pe that after all these times, I am not too rusty to set good tas<span style="color: red">k</span>s for yo<span style="color: red">u</span> to enjoy, starting with <span style="color: red">t</span>his <span style="color: red">o</span>ne! <strong>See yo<span style="color: red">u</span> in the round!</strong> <span style="color: #ec3e9d"><i>"Waeeguyehy" is coming soon.</i></span> </spoiler> It's been a while, today [user:AkiLotus,2024-07-29] and I are delighted to invite you to participate in [contest:2032]. This round will be <strong>rated</strong> for all participants with a rating lower than <...

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Solutions for Codeforces Beta Round #74 <p><b>A div2</b>. In this problem you can <span id="result_box" class="short_text" lang="en"><span title="Нажмите, чтобы увидеть альтернативный перевод" class="hps">simulate the</span> <span title="Нажмите, чтобы увидеть альтернативный перевод" class="hps">process. You can consider all minutes and in </span></span><span id="result_box" class="short_text" lang="en"><span title="Нажмите, чтобы увидеть альтернативный перевод" class="hps">dependence by a color of a current cablecar decrease size of </span></span>corresponding group of students $G$ by<span id="result_box" class="short_text" lang="en"><span title="Нажмите, чтобы увидеть альтернативный перевод" class="hps"></span></span> $min(|G|,2)$, where $|G|$ is size of the group. After that you should determine the first minute $t$ in that all three groups of students will be empty. So $t+30$ is an answer. This solution works in $O(r+g+b)$.<br>[cut]<br>Also there is $O(1)$ solution. It is following formula: $ans = max(3[(R+1)/2] + 27, 3[...

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My ideas for codeforces 27 Here's my algorithms and ideas:<div><br></div><div><span class="Apple-style-span" style="color: rgb(51, 51, 51); font-family: 'Courier New', Courier, FreeMono, monospace; font-size: 15px; line-height: 20px; ">Hi guys.<div>Codeforces beta round #27 just finished. It was a great contest. I really enjoyed it.</div><div>Here is the problems:</div><div><a href="http://mirror.codeforces.com/contest/27" style="text-decoration: none; color: rgb(102, 102, 204); ">http://mirror.codeforces.com/contest/27</a></div><div>let's take a look at them and see if they can be solved.</div><div><br></div><div>We start at problem A:</div><div><a href="http://mirror.codeforces.com/contest/27/problem/A" style="text-decoration: none; color: rgb(102, 102, 204); ">http://mirror.codeforces.com/contest/27/problem/A</a></div><div>We're given a set of numbers and we want to find the smallest number which is not in the list. This is easy. Take a boolean array of size 3000 and name it a. we assume a[i]=true iff i is present in the set. It's easy to u...

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Hackers ranking (beta) ### FAQ **What is this?** Have you ever wondered who is the best hacker on Codeforces? Here is simple solution, which would try to answer for your problem! I would like to introduce new system of grading hackers in rounds. [cut] <p></p> <b>How does it work?</b> The whole rating system is based on <a href="http://en.wikipedia.org/wiki/Elo_rating">Elo rating</a>. The problem is how to measure user's performance in each round. **Yes, how?** The whole system is now in phase of testing, so some solutions may be changed (and probably will be changed :)). So let's consider some user during some round. Let's call him Bob. **I want to choose another name, may I?** No. **Ok.** So, let's say that Bob solved three problems: A, B and C (Bob is pretty sad), but also hacked one solution for B and had one unsuccessful hack attempt. Bob doesn't know that his solution for C won't pass system tests. How would we know if it was good or bad? At first, we will look at al...

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Discussions Of CodeForces Round <h2 style="text-align: center;"><u>CodeForces Round</u></h2><div><u><br></u></div><div><a href="http://mirror.codeforces.com/blog/entry/84">CodeForces Beta Round 1</a><br></div><div><br></div><div><a href="http://mirror.codeforces.com/blog/entry/97">CodeForces Beta Round 2</a></div><div><br></div><div><a href="http://mirror.codeforces.com/blog/entry/141">CodeForces Beta Round 3</a></div><div><br></div><div><a href="http://mirror.codeforces.com/blog/entry/158">CodeForces Beta Round 4</a></div><div><br></div><div><a href="http://mirror.codeforces.com/blog/entry/196">CodeForces Beta Round 5</a></div><div><br></div><div><a href="http://mirror.codeforces.com/blog/entry/220">CodeForces Beta Round 6</a></div><div><br></div><div><a href="http://mirror.codeforces.com/blog/entry/239">CodeForces Beta Round 7</a></div><div><br></div><div><a href="http://mirror.codeforces.com/blog/entry/258">CodeForces Beta Round 8</a></div><div><br></div><div><a href="http://mirror.codeforces.com/blog/entry/276">CodeForces Beta Round 9</a></div><div><br></div><div><a href="ht...

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Codeforces Beta Round #85: Editorial <p class="MsoNormal"><font class="Apple-style-span" face="Arial"></font></p><p class="MsoNormal" style="mso-layout-grid-align:none;text-autospace:none"><font class="Apple-style-span" face="Arial"><span class="apple-style-span"><span style="font-family:Arial;color:black">Here you can find solutions to the problems from the past round. Editorial for Problem D (Div 1) was prepared by&nbsp;</span></span><span class="Apple-style-span" style="border-collapse: collapse; font-family: verdana, arial, sans-serif; font-size: 14px; "><a href="http://mirror.codeforces.com/profile/sdya" title="Colonel sdya" class="rated-user user-red" style="font-family: arial; text-decoration: none !important; font-weight: bold; color: rgb(0, 0, 204); ">sdya</a>.&nbsp;</span></font></p><p> <p class="MsoNormal"><font class="Apple-style-span" face="Arial"></font></p><p class="MsoNormal" style="mso-layout-grid-align:none;text-autospace:none"><font class="Apple-style-span" face="Arial"><span class="Apple-style-span" style="f...

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Problem Set Analysis Of CodeForces <b>Tutorial Links:<span class="Apple-tab-span" style="white-space:pre"> </span>&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;</b><div><a href="http://mirror.codeforces.com/blog/entry/85">Code Forces Beta Round 1 Tutorial</a><br><br><a href="http://mirror.codeforces.com/blog/entry/109">Code Forces Beta Round 2 Tutorial</a><br><br><a href="http://mirror.codeforces.com/blog/entry/107">Code Forces Beta Round 2 Another Tutorial</a><br><br><div>Code Forces Beta Round 3 Tutorial:</div><div><br><a href="http://mirror.codeforces.com/blog/entry/178">Code Forces Beta Round 4 Tutorial</a><br><br></div><div><a href="http://mirror.codeforces.com/blog/entry/213">Code Forces Beta Round 5 Tutorial</a></div><div><br></div><div>Code Forces Beta Round 6 Tutorial</div><div><br></div><div>Code Forces Beta Round 7 Tutorial</div><div><br></div><div>Code Forces Beta Round 8 Tutorial</div><div><br></div><div><a href="http://mirror.codeforces.com/blog/entry/283">Code Forces Beta Round 9 Tutorial</a><br><br></div><div>Code Forces Beta Round 10 Tutorial</div...

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Codeforces Beta Round #91 <p>Hello!<br /></p><p>Wellcome to <b>Codeforces Beta Round #91!</b>&nbsp;This time, the author of the round will be me, Herasymiv Vitaliy ([[user:witua,2011-10-26]]). Thanks a lot to Artem Rakhov ([[user:RAD,2011-10-26]]) for helping in round preparing and Maria Belova for problems translation. I hope you will like problems.</p><p>Good luck!</p><p>Thanks all! And here are the winners:</p><p>Division 1:</p><p><ol><li>[[user:tourist,2011-10-27]]</li><li>[[user:Rizvanov,2011-10-27]]</li><li>[[user:kuniavski,2011-10-27]]</li><li>[[user:Petr,2011-10-27]]</li><li>[[user:vepifanov,2011-10-27]]</li><li>[[user:dzhulgakov,2011-10-27]]</li><li>[[user:e-maxx,2011-10-27]]</li></ol></p><div>Division 2:</div><div><ol><li>[[user:trangpham,2011-10-27]]</li><li>[[user:liuq901,2011-10-27]]</li><li>[[user:cfmode,2011-10-27]]</li><li>[[user:wefgef,2011-10-27]]</li></ol><div><a href="http://mirror.codeforces.com/blog/entry/2956">Here</a> is an editorial.</div></div>

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ALL CodeForces Rounds Tutorial <html> <body> <br /><br /> >>>>>>>**Hi I just Say Really Sorry For Delay in UPD This Blog...!**<br /><br /><br /> <u>This is not Complete</u> , but i try to find <b>all Tutorial codeforces round</b> and posted here , thanks in advance :D <br /><br />This post will <b> <span class="Apple-style-span" style="border-collapse: collapse;color: rgb(255,0,0);font-family: verdana , arial , sans-serif;font-size: 12.0px;"> UPD</span></span></b> after each contest . <span>If anyone have or writes any editorial that's</span> <b> <span> <span class="Apple-style-span" style="border-collapse: collapse;color: rgb(255,0,0);font-family: verdana , arial , sans-serif;font-size: 12.0px;"> not in here</span></span></b> , Plz post here for ALL . <br /><br /><b>UPD </b> &nbsp;: Table1 updated : in Future!!! <br /><br /><b>UPD </b>&nbsp;: Table2 updated : CF # 118 ...to... CF # 169 added .<br /><br /> </p><hr /><br /></p> <div align="justify"> <br /><br /><b><s...

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Solutions to Codeforces Beta Round #27, A, B, C, D, E A. Next Test As the range of input size is only up to 3000, we can maintain an array to indicate which number has appeared in the given test. Then, we enumerate this array from index 1 to n, and the first number that cannot be found is the answer. B. Tournament It seems that there exist some other simpler methods than mine... The key idea of my solution is to build a directed graph. The players can be viewed as nodes in a directed graph, and node A has en edge directed to node B if we can find a match in which A wins against B. Then, we can maintain an array to count the number of matches that a player has participated in. It is straightforward that we will find out two players who have only participated in n-2 matches while the other ones all have participated in n-1 matches. After finding out the two players, without of loss generality, we denote them as A and B, and then we implement "graph traversal" for two times witht the starting point as A and B, respectively. If we ca...

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Blog collection <p>________________________________________________________________________________________<br><br></p><h3><b>Puzzle</b></h3><ul><li><a href="http://mirror.codeforces.com/blog/entry/66">Red and Black hair</a>, </li><li><a href="http://mirror.codeforces.com/blog/entry/112">The 12 chairs and diamonds</a></li><li><a href="http://mirror.codeforces.com/blog/entry/228">Monty Hall Problem</a></li></ul><br><br><h3>Useful <br></h3><ul><li><a href="http://mirror.codeforces.com/blog/entry/70">Petr Mitrichev, 3 days in Sao Paulo Training Camp 2010</a></li><li><a href="http://mirror.codeforces.com/blog/entry/512">Useful links</a></li><li><a href="http://mirror.codeforces.com/blog/entry/529">Problem Set Analysis Of CodeForces</a></li><li><a href="http://mirror.codeforces.com/blog/entry/546">Discussions Of CodeForces Round</a></li><li><a href="http://mirror.codeforces.com/blog/entry/1492">ALL CodeForces rounds Tutorial</a></li><li><a href="http://mirror.codeforces.com/blog/entry/1534">Online Judge Locator</a></li><li><a href="http://mirror.codeforces.com/blog/entry/170...

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Micro- and macro-management for your next cpp source: General tips'n'tricks Hello, Codeforces! In this series of articles, I would like to tell you about tips'n'tricks I use in C++ sources. Some of them require a strong C++ background, some not, but all of them are aimed to reduce the time you spend on basic things like reading input/debugging/etc, so it might be useful for your next template. This part is dedicated to some basic tips (and probably should've been the first part but it's not ¯\\_(ツ)_/¯). <spoiler summary="TL;DR"> Full code: ~~~~ #include <bits/stdc++.h> using namespace std; using i64 = int64_t; using f80 = long double; using Str = string; template <class T> using Vec = vector<T>; template <class K, class V> using UM = unordered_map<K, V>; template <class T> auto &operator>>(istream &is, vector<T> &xs) { for (auto &x : xs) is >> x; return is; } namespace io { template <class ...As> auto &read(As &...as) { return (cin >> ... >> as); } template <class ...As> auto &log(const As &...as) { return ((cerr << " " << as...

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