As discussed in my previous blog, we are going to introduce a new system for Rated/Unrated participation. It will take effect from this weekend's contests (ABC, AGC, and ARC). See this post for details.

If you have any questions, please leave them here.

We will hold AtCoder Regular Contest 130.

• Contest URL: https://atcoder.jp/contests/arc130
• Start Time: http://www.timeanddate.com/worldclock/fixedtime.html?iso=20211128T2100&p1=248
• Duration: 120 minutes
• Number of Tasks: 6
• Writer: maspy
• Tester: HIR180, tempura0224
• Rated range: — 2799

The point values will be 300-400-500-600-800-1000.

We are looking forward to your participation!

We will hold AtCoder Regular Contest 129.

• Contest URL: https://atcoder.jp/contests/arc129
• Start Time: http://www.timeanddate.com/worldclock/fixedtime.html?iso=20211121T2100&p1=248
• Duration: 120 minutes
• Number of Tasks: 6
• Writer: maroonrk
• Tester: maspy, satashun
• Rated range: — 2799

The point values will be 300-400-500-600-900-1000.

We are looking forward to your participation!

We will hold Daiwa Securities Co. Ltd. Programming Contest 2021（AtCoder Regular Contest 128）.

• Contest URL: https://atcoder.jp/contests/arc128
• Start Time: http://www.timeanddate.com/worldclock/fixedtime.html?iso=20211016T2100&p1=248
• Duration: 120 minutes
• Number of Tasks: 6
• Writer: maroonrk
• Tester: maspy, yamunaku
• Rated range: — 2799

The point values will be 400-400-600-700-800-1000.

We are looking forward to your participation!

We will hold AtCoder Regular Contest 127.

Please note the unusual start time (1 hour earlier than usual).

• Contest URL: https://atcoder.jp/contests/arc127
• Start Time: http://www.timeanddate.com/worldclock/fixedtime.html?iso=20210925T2000&p1=248
• Duration: 120 minutes
• Number of Tasks: 6
• Writer: maroonrk
• Tester: maspy, tempura0224
• Rated range: — 2799

The point values will be 300-500-500-700-800-1000.

We are looking forward to your participation!

We will hold AtCoder Regular Contest 126. Please note the unusual start time (1 hour later than usual)

• Contest URL: https://atcoder.jp/contests/arc126
• Start Time: http://www.timeanddate.com/worldclock/fixedtime.html?iso=20210919T2200&p1=248
• Duration: 120 minutes
• Number of Tasks: 6
• Writer: maspy
• Tester: satashun, tempura0224
• Rated range: — 2799

The point values will be 300-400-600-600-800-1100.

We are looking forward to your participation!

We will hold AtCoder Regular Contest 125.

• Contest URL: https://atcoder.jp/contests/arc125
• Start Time: http://www.timeanddate.com/worldclock/fixedtime.html?iso=20210822T2100&p1=248
• Duration: 120 minutes
• Number of Tasks: 6
• Writer: maroonrk
• Tester: maspy, yamunaku
• Rated range: — 2799

The point values will be 300-500-600-700-800-900.

We are looking forward to your participation!

We will hold AtCoder Regular Contest 124.

• Contest URL: https://atcoder.jp/contests/arc124
• Start Time: http://www.timeanddate.com/worldclock/fixedtime.html?iso=20210725T2100&p1=248
• Duration: 120 minutes
• Number of Tasks: 6
• Writer: camypaper
• Tester: tatyam, maspy
• Rated range: — 2799

The point values will be 300-400-500-700-800-900.

We are looking forward to your participation!

We will hold AtCoder Regular Contest 123.

• Contest URL: https://atcoder.jp/contests/arc123
• Start Time: http://www.timeanddate.com/worldclock/fixedtime.html?iso=20210718T2100&p1=248
• Duration: 120 minutes
• Number of Tasks: 6
• Writer: maspy
• Tester: tatyam, tempura0224
• Rated range: — 2799

The point values will be 300-400-600-700-700-1000.

We are looking forward to your participation!

We will hold AtCoder Grand Contest 054. This contest counts for GP30 scores.

• Contest URL: https://atcoder.jp/contests/agc054
• Start Time: http://www.timeanddate.com/worldclock/fixedtime.html?iso=20210627T2100&p1=248
• Duration: 150 minutes
• Number of Tasks: 6
• Writer: yosupo, sigma425, maroonrk, wo_
• Tester: satashun, HIR180
• Rated range: 1200 -

The point values will be 300-800-800-1000-1200-1800.

We are looking forward to your participation!

After the last ARC, one participant pointed out that the result is WA when the error is precisely the same as $$$EPS$$$ (submission).

For example, consider these two outputs: 331997010.50000000000000000000 (the jury output) and 331997342.4970105 (the user output). Their relative error is exactly $$$10^{-6}$$$, so when $$$EPS=10^{-6}$$$, this should get AC.

However, with the current implementation of the doubleCompare function in testlib.h, the result is WA. This is because perturbations in the line 429 (return result + 1E-15 >= minv && result <= maxv + 1E-15;) don't work when the values of result/minv/maxv are large. We made a fix and sent a pull request.

If you believe you were affected by this in the last ARC, please let me know.

That being said, given the popularity of testlib.h and the fact that no one has ever raised this issue, I hope no one was affected by this in the entire history of testlib.h.

We will hold Tokio Marine & Nichido Fire Insurance Programming Contest 2021（AtCoder Regular Contest 122).

• Contest URL: https://atcoder.jp/contests/arc122
• Start Time: http://www.timeanddate.com/worldclock/fixedtime.html?iso=20210612T2100&p1=248
• Duration: 120 minutes
• Number of Tasks: 6
• Writer: maroonrk
• Tester: maspy, yamunaku
• Rated range: — 2799

The point values will be 400-500-600-700-800-1200.

We are looking forward to your participation!

As of now, there is no blog, so I'll post this.

How to solve C Large without complex casework?

We will hold NOMURA Programming Contest 2021(AtCoder Regular Contest 121).

• Contest URL: https://atcoder.jp/contests/arc121
• Start Time: http://www.timeanddate.com/worldclock/fixedtime.html?iso=20210529T2100&p1=248
• Duration: 120 minutes
• Number of Tasks: 6
• Writer: camypaper
• Tester: maspy, yamunaku
• Rated range: — 2799

The point values will be 400-500-500-700-700-800.

We are looking forward to your participation!

Please note that the contest time is one hour earlier than the usual time.

We will hold AtCoder Regular Contest 120.

• Contest URL: https://atcoder.jp/contests/arc120
• Start Time: http://www.timeanddate.com/worldclock/fixedtime.html?iso=20210523T2000&p1=248
• Duration: 120 minutes
• Number of Tasks: 6
• Writer: QCFium
• Tester: maspy, satashun
• Rated range: — 2799

The point values will be 400-400-500-600-700-1600(800).

The full version of the last problem is unusually hard for ARC, so there is an 800-point subtask.

We are looking forward to your participation!

We will hold AtCoder Regular Contest 119.

• Contest URL: https://atcoder.jp/contests/arc119
• Start Time: http://www.timeanddate.com/worldclock/fixedtime.html?iso=20210516T2100&p1=248
• Duration: 120 minutes
• Number of Tasks: 6
• Writer: E869120, square1001
• Tester: maspy
• Rated range: — 2799

The point values will be 300-500-500-700-800-800.

We are looking forward to your participation!

Please note the unusual start time.

We will hold AtCoder Regular Contest 118.

• Contest URL: https://atcoder.jp/contests/arc118
• Start Time: http://www.timeanddate.com/worldclock/fixedtime.html?iso=20210509T2205&p1=248
• Duration: 120 minutes
• Number of Tasks: 6
• Writer: maspy
• Tester: tempura0224, yamunaku
• Rated range: — 2799

The point values will be 300-400-500-700-800-1000.

We are looking forward to your participation!

We will hold AtCoder Regular Contest 117.

• Contest URL: https://atcoder.jp/contests/arc117
• Start Time: http://www.timeanddate.com/worldclock/fixedtime.html?iso=20210418T2100&p1=248
• Duration: 120 minutes
• Number of Tasks: 6
• Writer: E869120, square1001
• Tester: tempura0224
• Rated range: — 2799

The point values will be 200-400-600-600-900-900.

We are looking forward to your participation!

We will hold AtCoder Grand Contest 053. This contest counts for GP30 scores.

• Contest URL: https://atcoder.jp/contests/agc053
• Start Time: http://www.timeanddate.com/worldclock/fixedtime.html?iso=20210410T2100&p1=248
• Duration: 180 minutes
• Number of Tasks: 6
• Writer: yutaka1999
• Tester: HIR180
• Rated range: 1200 -

The point values will be 400-700-900-1000-1400-2400.

We are looking forward to your participation!

We will hold AtCoder Regular Contest 116.

• Contest URL: https://atcoder.jp/contests/arc116
• Start Time: http://www.timeanddate.com/worldclock/fixedtime.html?iso=20210328T2100&p1=248
• Duration: 120 minutes
• Number of Tasks: 6
• Writer: kort0n
• Tester: beet, heno239, tempura0224
• Rated range: — 2799

The point values will be 300-400-500-500-800-800.

We are looking forward to your participation!

We will hold AtCoder Regular Contest 115. Please watch out for the unusual start time (1 hour earlier).

• Contest URL: https://atcoder.jp/contests/arc115
• Start Time: Unusual Start Time (1 hour earlier) http://www.timeanddate.com/worldclock/fixedtime.html?iso=20210321T2000&p1=248
• Duration: 120 minutes
• Number of Tasks: 6
• Writer: YoshikaMiyafuji
• Tester: maspy, yamunaku
• Rated range: — 2799

The point values will be 300-400-500-600-700-1000.

We are looking forward to your participation!

We will hold AtCoder Regular Contest 114.

• Contest URL: https://atcoder.jp/contests/arc114
• Start Time: http://www.timeanddate.com/worldclock/fixedtime.html?iso=20210314T2100&p1=248
• Duration: 120 minutes
• Number of Tasks: 6
• Writer: satashun
• Tester: gazelle, kobae964
• Rated range: — 2799

The point values will be 300-400-600-600-700-900.

We are looking forward to your participation!

XXI Opencup GP of Tokyo will be held tomorrow.

I prepared the problems with the help from hos.lyric.

I'll upload the editorial after the contest ends, and also I'll upload the contest to the GYM.

Editorial

GYM

We will hold AtCoder Regular Contest 113.

• Contest URL: https://atcoder.jp/contests/arc113
• Start Time: http://www.timeanddate.com/worldclock/fixedtime.html?iso=20210221T2100&p1=248
• Duration: 120 minutes
• Number of Tasks: 6
• Writer: DEGwer, maroonrk
• Tester: latte0119, reew2n
• Rated range: — 2799

The point values will be 300-400-500-600-800-1000.

We are looking forward to your participation!

We will hold AtCoder Regular Contest 112.

• Contest URL: https://atcoder.jp/contests/arc112
• Start Time: http://www.timeanddate.com/worldclock/fixedtime.html?iso=20210213T2100&p1=248
• Duration: 120 minutes
• Number of Tasks: 6
• Writer: nuip, potetisensei
• Testers: latte0119 reew2n
• Rated range: — 2799

The point values will be 300-400-500-600-700-900.

We are looking forward to your participation!