By dotorya, history, 32 hours ago, In English,

Recently, There seems to be so many multiple accounts among various rating ranges.

In top 10, there is CongLingDanPaiShang3k5, who became Legendary Grandmaster in 2 months. He should be a great genius, right? There is better hypothesis: He is someone's smurfing account.

Everybody knows that jiry_2 = Syloviaely. He performed quite a long ago, but it's the fact that he has multiple accounts, both having 2900+ ratings.

In Div2 contests, many black-colored people are at top of the scoreboards. Why there are always a lot of talented newcomers? You will know the reason.

Why don't Codeforces ban those multiple accounts? They ruins contest scoreboard and rating system. For example, CongLingDanPaiShang3k5 "absorbed" other participants rating for about 5-6 contests to be Legendary Grandmaster. On those contest's scoreboard, there were always him on top pages.

One account for one person. That was the rule. Smurfing accounts should be banned.

Read more »

 
 
 
 
  • Vote: I like it  
  • +773
  • Vote: I do not like it  

By ch_egor, 2 days ago, translation, In English,

Hi everybody,

This Sunday there will be a 16th Moscow Team Olympiad, high school students competition based in Moscow that is an elimination contest for All-Russian Team Olympiad. This contest is prepared by Moscow Olympiad Scientific Committee that you may know by Moscow Open Olympiad, Moscow Olympiad for Young Students and Metropolises Olympiad (rounds 327, 342, 345, 376, 401, 433, 441, 466, 469, 507).

Round will be held at 10:05 UTC on Sunday and will last for 2 hours. Each division will have 6 problems.

Problems are prepared gritukan, Glebodin, Andreikkaa, qoo2p5, mingaleg, Flyrise, _kun_, achulkov2, grphil, Sehnsucht, Aphanasiy, Sender, DebNatkh, GreenGrape under my supervision with great help of GlebsHP, _meshanya_, Endagorion, Zlobober and Helen Andreeva.

Thanks to _kun_ for the round coordination and statement translation, and also thanks for MikeMirzayanov for systems codeforces and polygon, which was used to prepare problems of this olympiad.

Good luck everybody!

UPD1: The scoring distribution will be:

500 — 10001000 — 1500 — 2000 — 2500 for div. 1.

500 — 1000 — 1500 — 20002000 — 2500 for div. 2.

UPD2: Editorial

Read more »

 
 
 
 
  • Vote: I like it  
  • +173
  • Vote: I do not like it  

By MikeMirzayanov, 3 days ago, translation, In English,

Hi Codeforces!

For you, perhaps it was yet another Codeforces round. But not for me. Codeforces Round #515 (Div. 3) is the first round tested on new judging servers at ITMO University. And this is not just an update of location. Ta-dam! Now your solutions will be judged on the new Intel i3-8100 processors. And this is not all news. The number of judging servers has increased, which means fewer queues during rounds!

I am pleased to announce that now I live in St. Petersburg, I work at ITMO, and Codeforces is gradually moving from the walls of dear to me Saratov University to ITMO University. The decision to move was not easy for me. My plan is that, based on ITMO, I can focus more on Codeforces development and work on the platform. The number of world champions per square meter is simply overwhelming, and working with a large team of such enthusiasts (and professionals!) of sports programming, like me, is extremely inspiring. I always liked St. Petersburg and the atmosphere of ITMO. Intuition did not let me down. I feel surrounded by people close to me in spirit (and I’m not only talking about a work). I am sure there are many interesting common projects ahead!

I do not say goodbye to Saratov. This is my hometown, full of people dear to me. I came to my first programming training at SSU exactly 20 years ago. Antonina Fedorova, thank you very much. Natalya Andreeve, I would like to say a personal thank you now. You have opened for me an interesting world of programming competitions. We were happy together when we first advanced to the ICPC Finals, and later when we became champions of Russia and the World. We made countless competitions and helped many Saratov students find themselves in programming. I fervently support the future of the Programming Competitions Training Center at SSU and future generations of Saratov contest participants. And now, I am in Saratov and still the head of the jury of the ICPC Subregional Contest, and even an SSU employee. I hope that we will make a good and interesting contest.

I will try to make a complete relocation of the Codeforces infrastructure to ITMO without downtimes. A good Internet connection between SSU and ITMO is encouraging. All the planned work will adapt to the schedule of the rounds, and now it pleases more than ever (I send my greetings to the coordinators!).

Currently, all Codeforces and Polygon solutions are being judged on new servers based on Intel i3-8100 processors. Fortunately, the performance of a single core is not very different from the one that the old generation of judging servers had. Thus, the time limits in all problems remain the same.

Such news. I am waiting for you on Codeforces Round #516 (by Moscow Team Olympiad).

MikeMirzayanov

Read more »

 
 
 
 
  • Vote: I like it  
  • +1232
  • Vote: I do not like it  

By _kun_, history, 33 hours ago, translation, In English,

Credits:

Div2A (Make a Trianle): Idea by Zlobober, development by gritukan

Div2B (Equations of Mathematical Magic): Idea and development: Glebodin

Div1A (Oh Those Palindromes): Idea by Endagorion, development by Andreikkaa

Div1B (Labyrinth): Idea and development by qoo2p5

Div1C (Dwarves, Hats and Extrasensory Abilities): Idea and development by mingaleg

Div1D (Candies for Children): Idea by Endagorion, development by Flyrise

Div1E (Lasers and Mirrors): Idea and development by mingaleg

Div1F (String Journey): Original idea by GreenGrape, solution by gritukan, development gritukan and GreenGrape

Tutorial is loading...
Tutorial is loading...
Tutorial is loading...
Tutorial is loading...
Tutorial is loading...
Tutorial is loading...
Tutorial is loading...
Tutorial is loading...

Read more »

 
 
 
 
  • Vote: I like it  
  • +37
  • Vote: I do not like it  

By ko_osaga, history, 3 days ago, In English,

OpenCup GP of Korea (third edition) is scheduled at 2018/10/14 Sunday, 11:00 MSK.

Both Div1 / Div2 problemset will feature Korean problems.

Problemsetters: ainta alex9801 Cauchy_Function HYEA jh05013 ko_osaga OnionPringles Togekiss .o.

Enjoy!

Read more »

Tags gp, of, korea
 
 
 
 
  • Vote: I like it  
  • +105
  • Vote: I do not like it  

By ivan100sic, history, 3 days ago, In English,

I've never seen anyone use this in competitive programming (or anywhere really) but it might be useful:

In C++ you can use the basic_string class template instead of vector for "simple" types [1]. It works just like vector but also allows you to use a few convenient member functions and operators just like with strings, most notably operator+ and operator+=. See the following code:

#include <bits/stdc++.h>
using namespace std;

int main() {
    int n;
    basic_string<int> a;

    cin >> n;
    for (int i=0; i<n; i++) {
        int x;
        cin >> x;
        a += x;
    }

    a += a;
    a = a.substr(n/2, n);

    cout << (a + a).find({1, 2, 1}) << '\n';
}

[1] Although I'm not 100% sure, "simple" is any primitive type, std::pair of simple types, etc. Do not use this with vectors, strings, sets, maps and similar types. And for this reason please don't typedef vector as basic_string.

Read more »

 
 
 
 
  • Vote: I like it  
  • +238
  • Vote: I do not like it  

By Errichto, history, 3 hours ago, In English,

Hi.

There is a new game where you can win $10k for writing the best bot for a 2-player game Terminal: https://terminal.c1games.com. There are some smaller local competitions, mainly for universities. In short, it's a tower-defense game where you build towers to defend against minions sent by your opponent, and at the same time you attack with minions too.

I have some experience with games like this (we had a few 24-hour game-bot competitions in Poland), so I think I can share some knowledge and intuition. I will stream on Wednesday (1pm CEST), Friday and Sunday. You can see the exact time on my Youtube channel as a scheduled event. If you miss it, you can watch a video later.

I talked with contest organizers and they encourage the stream, but ofc. don't expect to hear something enough to get top1.

See you.

Read more »

 
 
 
 
  • Vote: I like it  
  • +34
  • Vote: I do not like it  

By touristic, history, 33 hours ago, In English,

Screenshot from ~9 years ago Codeforces Beta! http://funkyimg.com/i/2M6zq.png Copyrights to my friend

Read more »

 
 
 
 
  • Vote: I like it  
  • +75
  • Vote: I do not like it  

By neal, 4 days ago, In English,

C++ has always had the convenient data structures std::set and std::map, which are tree data structures whose operations take time. With C++11, we finally received a hash set and hash map in std::unordered_set and std::unordered_map. Unfortunately, I've seen a lot of people on Codeforces get hacked or fail system tests when using these. In this post I'll explain how it's possible to hack these data structures and what you can do in order to continue using your favorite hash maps without worrying about being hacked

Read more »

 
 
 
 
  • Vote: I like it  
  • +644
  • Vote: I do not like it  

By silversnitch, history, 15 hours ago, In English,

Hey there, I tried submitting solution to 1064D during the contest. My solution can be found here. As many of you might have noticed the solution is incorrect, I was expecting WA verdict but got RTE (on pretest 8 to be precise). I tried searching a lot but could not figure out why it was RTE and not WA. The exit code was -1073741571 if it helps.Can anyone help me with the solution(Not solution to the problem but why there was a RTE verdict). Thank You

Read more »

 
 
 
 
  • Vote: I like it  
  • +4
  • Vote: I do not like it