AtCoder Regular Contest (ARC) will primarily be held in the traditional format (rated 1200–2799) starting from ARC215. Div.1/Div.2 will be renamed to "AtCoder Regular Contest ++" / "AtCoder Regular Contest --" respectively, and will continue to be held. The format for each Division will be adjusted as follows. ## Contest Format - ARC++ - Rated range: <span class="user-blue">1600</span>–<span class="user-red">2999</span> - Contest duration: 150 minutes - Problems: 4–5 problems worth approximately 600–1000 points - ARC - Rated range: <span class="user-cyan">1200</span>–<span class="user-orange">2799</span> - Contest duration: 120 minutes - Problems: 5–6 problems worth approximately 400–800 points - ARC-- - Rated range: <span class="user-green">800</span>–<span class="user-yellow">2399</span> - Contest duration: 120 minutes - Problems: 6–7 problems worth approximately 300–700 points The annual target is to hold ARC++ 5 times, ARC 10 times, and ARC-- 5 times per year. ## Scoring Criteria The scoring criteria for future ARCs are as follows. (This differs from the scoring criteria for ABC and AGC.) |Score|Optimal Target Rating Range| |:--:|:--:| |300|<span class="user-brown">400</span>–<span class="user-brown">799</span>| |400|<span class="user-green">800</span>–<span class="user-green">1199</span>| |500|<span class="user-cyan">1200</span>–<span class="user-cyan">1599</span>| |600|<span class="user-blue">1600</span>–<span class="user-blue">1999</span>| |700|<span class="user-yellow">2000</span>–<span class="user-yellow">2399</span>| |800|<span class="user-orange">2400</span>–<span class="user-orange">2799</span>| |900|<span class="user-red">2800</span>–<span class="user-red">3199</span>| |1000–|<span class="user-red">3200</span>–| <span class="grey">* "Optimal Target Rating Range" refers to the rating range at which approximately half of the participants are expected to solve the problem. Designing and measuring an absolute difficulty metric is difficult, hence this intentionally vague phrasing. (For example, solve rates are affected by the other problems in the same set.)</span> Scores are determined by the admin taking into account not only the expected difficulty but also various factors such as problem type and set balance, so the above criteria are merely a reference. ## Background <details> <summary>This section is long; read only if you are interested.</summary> <h3 id="2025-">Looking Back on 2025</h3> <p>The main goals of the Division system were the following two points.</p> <ul> <li>To more smoothly bridge the gap between ABC and AGC by separating into a more competitive Div.1 and a more casual Div.2.</li> <li>To hold ARC (Div.1) contests that would be exempt from the generative AI rules.</li> </ul> <p>Over the course of 2025, the following changes occurred.</p> <ul> <li>By raising the rated upper limit of Div.1, it became easier to differentiate the role of each Division.</li> <li>Div.1 also became subject to the <a href="https://info.atcoder.jp/entry/llm-rules-en">AtCoder Generative AI Rules</a>, and the latter goal was no longer fulfilled.</li> </ul> <p>After running the Division system for a year, both achievements and challenges became clear.</p> <ul> <li><p>Achievements:</p> <ul> <li>By making Div.1 more competitive, there were more rated contests for competitors rated 2800–2999.</li> <li>Being able to change the Division based on writers' drafts made it easier to hold contests.</li> </ul> </li> <li><p>Challenges:</p> <ul> <li>The rated range became narrower than before, reducing the number of people who could enjoy rated contests.<ul> <li>While this is somewhat unavoidable for the more competition-focused Div.1, we would like to improve this for the more casual Div.2.</li> </ul> </li> <li>There were frequent cases where a middle ground between Div.1 and Div.2 (rated for 1200–2799) would have been ideal. </li> </ul> </li> </ul> <h3 id="2026-">Policy for 2026</h3> <ul> <li>The main ARC will again be rated for 1200–2799.<ul> <li>The Division system was intended to last only until both "Div.1 also bans AI" and "one year has passed" were satisfied, so this is proceeding as planned.</li> </ul> </li> <li>The Division system will be retained.<ul> <li>We have gotten a sense that having 2–3 types of contests between ABC and AGC is about right.</li> </ul> </li> <li>The Division names will be changed.<ul> <li>The split into "Div.1, no Div, Div.2" is confusing.</li> <li>Taking the following constraints into account, we have adopted the naming "ARC++, ARC, ARC--".<ul> <li>We want the main 1200–2799 format to simply be called <code>AtCoder Regular Contest</code> as before.</li> <li>We want to avoid major name changes and maintain brevity by keeping (former) Div.1 and Div.2 under the ARC umbrella.</li> <li>We want the names to be easy to distinguish in conversation and on social media.</li> <li>Visibility & distinguishability. ("ARC+" and "ARC-" are harder to read, and writing things like "ARC+AGC" could be confusing.)</li> </ul> </li> </ul> </li> <li>The rated lower limit of ARC-- will be lowered to 800.<ul> <li>This makes (former) Div.2 more casual to differentiate it from ARC, while also expanding the range of people who can enjoy rated contests.</li> </ul> </li> <li>The difficulty of ARC and ARC-- will be lowered.<ul> <li>ARC will aim for a difficulty level at which a certain number of rated participants solve all problems.<ul> <li>"A certain number": approximately 0–10 for ARC++, 5–20 for ARC, and 10–50 for ARC--.</li> </ul> </li> </ul> </li> </ul> <p>author: snuke (ARC admin) </p> </details> ## Related Articles - [Restructuring of contests](https://atcoder.jp/posts/1281) - [Announcement Regarding ARC's Division System](https://atcoder.jp/posts/1365) - [Changes to the Rated Cap of ARC Div.1](https://atcoder.jp/posts/1434) - [Generative AI Rule Changes Regarding ARC Div. 1](https://atcoder.jp/posts/1514) - [Regarding Rule Changes in ABC, ARC and AGC Due to Technological Advancement of Generative AI](https://atcoder.jp/posts/1568)