MikeMirzayanov's blog

Please, don't use "Codeforces Round ..." for mashup training contests
By MikeMirzayanov, 23 months ago, In English

Hello, Codeforces!

Recently, we have repeatedly encountered the fact that community members get confused in rounds, mistaking unofficial training in mashups with a round, which is prepared by the Codeforces team and the writers together with our coordinators.

To make it a little clearer, I ask you not to use "Codeforces Round ..." in the names of unofficial training rounds (mashups). Probably, if you are doing a series of such rounds, then you better come up with your own naming — this will make it clearer to the audience.

P.S. If you see that any author has not noticed my appeal, then please let him know.

Thank you!

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Me Too
By MikeMirzayanov, 23 months ago, In English

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2021-2022 ICPC, NERC, Northern Eurasia Onsite (Unrated, Online Mirror, ICPC Rules, Teams Preferred)
By MikeMirzayanov, 2 years ago, In English

Hello.

In the meantime, the onsite event has already begun. You can follow the results at the link https://nerc.itmo.ru/archive/2021/standings.html (refrain from viewing if you want to plan to write a mirror and want the conditions as close as possible to the participants in the competition).

There is great news. This year it was possible to get together without any online participation. Teams write from one computer! Good old ICPC.

And I suggest you join the online mirror. It is designed for team participation by those who have passed the qualifying competitions. Ready to try? Use the link: 2021-2022 ICPC, NERC, Northern Eurasia Onsite (Unrated, Online Mirror, ICPC Rules, Teams Preferred).

Good luck!

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About CodeTON Round 1 Prizes Strikes Again
By MikeMirzayanov, 2 years ago, In English

Hello.

I started processing responses on the form where we collected your TON wallet addresses. Unfortunately, many winners did not complete the form. I contacted some of them in PM and it turned out that this was not intentional.

We are extending the deadline for completing the form until 2022-04-06 23:59:59 (UTC +3). Please, if you want to receive coins, then fill out the form. A valid address looks like a random 48-character string. To register a wallet, follow one of these links: https://tonkeeper.com/ or https://wallet.ton.org/

The form can be filled out at https://codeforces.com/userForm/203c74605996e40f

Coins will be received by those who are at the top-1000. Additionally, those who solved at least one problem in this round will receive 1 coin each. Details can be read at the link.

The form will be processed on April 7th. And in a week after it, we will send out coins. Please do not disturb me or the organizers with questions that are answered in this post.

Also I remind you about TON Smart Challenge contest aimed at contract source code optimization: https://t.me/toncontests/26 It's not too late to connect and try your hand

You can read more about this competition here:

TON Smart Challenge 1 →

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Help from NEAR for Our Community
By MikeMirzayanov, 2 years ago, In English

Hello, Codeforces.

We live in difficult times. And, unfortunately, our community is highly dependent on world events around us. Three years ago, it seemed easy to send a t-shirt anywhere in the world. Now it's a quest with many unknowns. Just a few months ago, it was not difficult to send a reward to the problem writer. But now, we are cut off from the outside world and regulated by multiple new laws.

And here it is very important not to lose, not to break what has already been done. Don't stand still, move forward. I am very glad and grateful to the problem writers and coordinators that in March we managed to hold 10 ratings (we held 9, come to participate in the tenth). Thanks to everyone who took part in the preparation!

And I want to share another great news. Our friends NEAR has come up with the initiative to support the community during this difficult time. We are pleased to announce that the upcoming rounds will be funded by NEAR, which will help with the payment of rewards to problem writers and coordinators. This is a timely and important help. Thanks!

It will be easier and faster for us if the problem writers or coordinators have the opportunity to accept a reward in the form of a cryptocurrency transfer. In this case, we are ready to transfer 25% more and make the transfer much faster. Oh, it's a pity we can't send t-shirts with crypto.

And I remind you that the next round (and Codeforces Round #780 (Div. 3)) is waiting for you) will take place very soon, on 31.03.2022 17:35 (Московское время). I hope to see you among the participants.

— Mike

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About CodeTON Round 1 Prizes
By MikeMirzayanov, 2 years ago, In English

TLTR: If you are in the top-1000 of CodeTON Round 1, then fill out the form by the link https://codeforces.com/userForm/203c74605996e40f. Also, anyone who solved at least one problem in the round can fill out it and get 1 TON airdrop. The deadline is 23:59:59 (UTC +3) 04.04.22.

Hello. Great news from the TON Team. I give them the floor.

Good news everyone!

We decided to celebrate the successful finish of the CodeTON round by airdropping all the people who have solved at least one of the problems (officially, practice and virtual participation don't count) of the CodeTON round. Such participants are eligible for 1 TON airdrop and a memorable NFT. Please do note that such NFT bears only symbolic value and is not entered to have any financial or investment value.

Please submit your TON wallet address via the link https://codeforces.com/userForm/203c74605996e40f if you are eligible for such an airdrop by 23:59:59 (UTC +3) 04.04.22.

Winners are more than welcome to provide organizers with the TON Wallet addresses to claim their prizes.

We also want to invite all of you to try yourself at TON Smart Challenge contest aimed at contract source code optimization: https://t.me/toncontests/26

You can read more about this competition here:

TON Smart Challenge 1 →

Thank you for taking your part, hope you enjoyed the round, looking forward to meeting you later!

TON Foundation

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Codeforces Global Rounds 2021: Final Results (GR13-GR18)
By MikeMirzayanov, 2 years ago, In English

Tomorrow will be the first global round of this year. And we are happy to sum up the results of last season. We announce the results!

We remind you that the global rounds are a joint initiative of XTX and Codeforces. We are happy to announce that they continue into the new year.

We hold 6 such rounds per year. All of them are open to both divisions. At each such round, 50 brand T-shirts were handed out, and we are happy to give T-shirts to all problem authors.

The prizes for the 6-round series are:

  • In each round top-100 participants get points according to the table.
  • The final result for each participant is equal to the sum of points he gets in the four rounds he placed the highest.
  • The best 20 participants over all series get sweatshirts and place certificates.

The final standings after six rounds (sorted by total points in four best placed rounds):

Place Contestant = GR 13 GR 14 GR 15 GR 16 GR 17 GR 18
1 Radewoosh 3291 291 1000 — 1000 1000 291
2 tourist 2815 135 403 1000 706 706 346
3 ksun48 2201 135 706 706 443 346 265
4 maroonrk 1894 1000 226 142 226 265 403
5 Petr 1730 575 — 497 — 575 83
6 Benq 1662 — 497 575 346 — 244
7 jiangly 1501 497 346 63 497 161 4
8 Um_nik 1199 176 575 346 102 34 —
9 dengyaotriangle 1094 — — — — 94 1000
10 gop2024 1065 706 — 176 70 54 113
11 duality 1045 277 371 186 211 — —
12 Golovanov399 1017 254 277 138 — 325 161
13 tatyam 969 — 291 161 325 29 192
14 hos.lyric 888 128 — 254 — 181 325
15 lumibons 871 325 — 265 — 176 105
16 aid 868 226 145 218 198 226 29
17 Subconscious 812 — — 171 125 403 113
18 Rewinding 767 — — — 192 — 575
19 sunset 742 371 — 371 — — —
20 gisp_zjz 725 — 153 198 60 277 97
21 yosupo 724 — — 4 — 14 706
22 SSRS_ 715 68 90 31 — 186 371
23 dlalswp25 707 204 161 — 131 211 92
24 QAQAutoMaton 700 — — — 575 — 125
25 kotatsugame 659 — 149 105 277 — 128
26 hitonanode 657 — 181 62 307 107 8
26 qazswedx2 657 403 — — — — 254
28 Ormlis 642 — 171 48 235 149 87
29 inaFSTream 641 — — — — 198 443
30 never_giveup 626 218 192 74 — 142 58
31 244mhq 625 — 218 291 116 — —
32 LayCurse 622 149 265 192 — 16 —
33 He_Ren 582 — — — 371 131 80
34 natsugiri 574 — 166 110 80 218 —
35 mango_lassi 555 119 135 97 204 11 —
36 LJC00118 523 198 325 — — — —
36 dreamoon_love_AA 523 — 52 307 72 92 37
38 Maksim1744 517 54 244 66 153 — —
39 VivaciousAubergine 515 — 72 443 — — —
40 yhx-12243 511 — 443 68 — — —
41 nuip 499 — — 166 90 171 72
42 QuietBeautifulThoughts 497 — — — — — 497
42 he_____hezhou 497 — — — — 497 —
44 SpyCheese 489 — — 46 — 443 —
44 snuke 489 — — 27 218 244 —
46 ugly2333 484 — 138 54 — 74 218
47 Toxel 468 90 — 76 — 254 48
48 AndreySergunin 444 244 78 122 — — —
49 RALZH 443 443 — — — — —
50 hank55663 420 — — — 63 235 122
51 NotaMotuaQAQ 417 110 307 — — — —
52 TadijaSebez 408 — 5 403 — — —
53 Alice_foo_foo 403 — — — 403 — —
54 Endagorion 399 211 1 17 — 166 5
55 Farhod 397 153 102 — 142 — —
56 ecnerwala 391 346 — 45 — — —
57 hanbyeol_ 390 — — — 291 99 —
58 dorijanlendvaj 385 10 — 52 166 — 157
59 zh0ukangyang 383 — — — — 157 226
60 blackbori 377 — 83 50 244 — —
61 huyinghao0706 371 — — — — 371 —
62 sansen 370 — — 116 254 — —
63 TLEwpdus 362 — 2 211 — — 149
64 Sugar_fan 351 235 116 — — — —
65 dario2994 350 94 128 — 58 — 70
66 tmwilliamlin168 348 — 41 — — 307 —
67 turmax 339 — 142 119 78 — —
68 ko_osaga 325 — — 325 — — —
69 Karry5307_AK_NOI2024 321 — — — — 110 211
70 TLE 320 — — — 149 — 171
71 heno239 312 — 176 70 — — 66
72 p_b_p_b 307 307 — — — — —
72 353cerega 307 52 — 153 — 102 —
72 HIR180 307 — — — — — 307
75 Marcin_smu 301 265 — — — 36 —
76 receed 300 102 198 — — — —
77 Alan233 299 — — — — 113 186
78 tute7627 297 — 27 58 — 70 142
79 Froggygua 291 — — — — 291 —
80 fanache99 288 — 131 — 105 52 —
81 Isonan 281 107 157 — — 17 —
82 KostasKostil 277 — — 277 — — —
82 MyBotDear 277 — — — — — 277
84 jiangly_fan 273 — — 157 116 — —
85 Rafbill 272 80 — — 87 105 —
86 mtsd 269 — — — — 138 131
87 fivedemands 265 — — — 265 — —
88 risujiroh 262 58 — — — — 204
89 Konijntje 257 — 22 — — — 235
89 Temotoloraia 257 — — 226 10 21 —
91 Elegia 254 — 254 — — — —
92 Worteltje 252 — — — — 192 60
93 Egor 244 — — 244 — — —
93 AliShahali1382 244 85 24 135 — — —
95 l1ll5 238 34 — — — 204 —
95 atomicenergy 238 46 16 — — 135 41
97 kotamanegi 235 — — 235 — — —
97 _h_ 235 — 235 — — — —
99 noimi 225 — 94 34 97 — —
100 potato167 216 — — 37 22 58 99
101 kmjp 215 — — 22 27 116 50
101 AutumnKite 215 — — — — 153 62
103 Argentina 212 — — — 186 — 26
104 ehnryx 211 — 211 — — — —
105 eatmore 210 116 — — — — 94
106 nocriz 204 — 204 — — — —
106 renascencepjw0510 204 — — 204 — — —
108 wasa855 202 — — — 26 — 176
108 fastmath 202 92 110 — — — —
108 amethyst0 202 181 — 21 — — —
111 errorgorn 199 — — 43 — 78 78
112 Froggay 198 — — — — — 198
113 ainta 195 — — — — 119 76
114 uwi 192 192 — — — — —
115 Geothermal 188 — — — 157 31 —
116 nantf 186 — 186 — — — —
116 YeongTree 186 186 — — — — —
118 voidmax 181 — — — 181 — —
118 Rainbow_qwq 181 — — — — — 181
118 scott_wu 181 — — 181 — — —
121 Torta 177 — — 80 — 97 —
122 nick452 176 — — — 176 — —
123 fedoseev.timofey 174 39 63 72 — — —
124 cnoi 171 — — — 171 — —
124 MAOooOAM 171 171 — — — — —
126 nutella_waxberry 166 166 — — — — —
126 PetelgeuseRomaneeconti 166 — — — — — 166
128 Nachia 164 138 — 26 — — —
129 Anadi 161 161 — — — — —
129 huhaoo 161 — — — 161 — —
131 Ra16bit 158 66 — — 92 — —
132 dsgrekova2 157 157 — — — — —
132 peti1234 157 — 125 — 32 — —
134 krijgertje 153 — 119 — — — 34
134 Y25t 153 — — — — — 153
136 Egor.Lifar 152 — 8 16 128 — —
137 isaf27 150 63 — 87 — — —
138 Swistakk 149 — — 149 — — —
139 Amoo_Safar 145 — — 145 — — —
139 ShuijunDainifei 145 — — — — 145 —
139 _FireBladeMaster_ 145 — — — — — 145
139 137_345_2814 145 — — — 145 — —
139 mnaeraxr 145 145 — — — — —
144 abc864197532 144 — — 125 — — 19
144 saba2000 144 125 — 19 — — —
146 ppavic 142 142 — — — — —
147 m_99 141 22 — — 119 — —
148 Xellos 140 — 92 — 48 — —
149 neal 138 — — — — — 138
149 why_no_girlfriend 138 — — — 138 — —
151 crackersamdjam 135 — — — 135 — —
151 gyh20 135 — — — — — 135
151 conqueror_of_tourist 135 50 37 — — 48 —
154 flashmt 131 — — 94 — 37 —
154 shb123 131 — — 131 — — —
156 oleh1421 130 — 4 — 94 — 32
157 qwerty787788 128 — — 128 — — —
157 Zhtluo 128 — — — — 128 —
159 Noam13 126 2 — 2 122 — —
160 Melania 125 — — — — 125 —
161 AlesyaIvanova 124 — 74 — 50 — —
162 Arayi 122 122 — — — — —
162 Hazyknight 122 — 122 — — — —
162 djq_cpp 122 — — — — 122 —
165 Suiseiseki 119 — — — — — 119
166 yuyue 116 — — — — — 116
166 Merkurev 116 — — — 116 — —
168 simonlindholm 113 — — 113 — — —
168 Yongaron 113 — 113 — — — —
168 chenyanbo 113 113 — — — — —
171 Pyqe 108 — 45 — 63 — —
172 Itst_boyfriend 107 — — 107 — — —
172 Tiramister 107 — 107 — — — —
172 asdsasd 107 — — — 107 — —
172 rama_pang 107 — — — — — 107
176 Wu_Ren 105 105 — — — — —
176 ix35 105 — 105 — — — —
178 Alex_2oo8 102 — — 102 — — —
178 chi1012 102 — — — — — 102
180 antontrygubO_o 99 — 99 — — — —
180 krismaz 99 — — 99 — — —
180 tabr 99 — — — 99 — —
180 Comet_Honeymoon 99 99 — — — — —
184 Vercingetorix 97 — — — — 41 56
184 donentseto 97 97 — — — — —
184 Suika_predator 97 — 97 — — — —
187 BurnedChicken 96 — — 60 29 7 —
188 Kodaman 92 — — 92 — — —
189 LiciaDu 90 — — 90 — — —
189 ljcleo 90 — — — — 90 —
189 TeaPot 90 76 — 14 — — —
189 Kubic 90 — — — — — 90
193 Aishiteru. 87 87 — — — — —
193 Enchom 87 — 87 — — — —
193 antekb 87 — — — — 87 —
196 God_Of_Blunder 85 — — — 85 — —
196 voover 85 — — 85 — — —
196 sumitacchan 85 — 85 — — — —
196 sys. 85 — — — — — 85
196 Morollcinna 85 — — — — 85 —
201 szhlg 83 83 — — — — —
201 skywalkert 83 — — 83 — — —
201 PubabaOnO 83 — — — — 83 —
201 ezLadder 83 — — — 83 — —
205 djq_fpc 80 — 80 — — — —
205 Roundgod 80 — — — — 80 —
207 SirShokoladina 78 78 — — — — —
207 scli_weapon 78 — — 78 — — —
209 C.S.T.T 76 — — — 76 — —
209 AoLiGei 76 — — — 76 — —
209 orzdevinwang 76 — 76 — — — —
209 dXqwq 76 — — — — 76 —
213 PinkieRabbit 74 — — — — — 74
213 prick 74 74 — — — — —
213 Savior-of-Cross 74 — 17 56 — 1 —
216 szb 72 72 — — — — —
216 KevinWan 72 — — — — 72 —
218 zscoder 71 37 — — 34 — —
219 hamlet 70 70 — — — — —
219 timmyfeng 70 — 70 — — — —
221 est_stella 68 — — — — — 68
221 happyguy656 68 — — — — 68 —
221 veckoper 68 — 68 — — — —
221 Izumi_Chiaki 68 — — — 68 — —
225 kektus 66 — 66 — — — —
225 awoo 66 — — — 66 — —
225 K_T_O 66 — — — — 66 —
228 Rubikun 63 — 39 — — 24 —
228 Kalptaru 63 — — — — 63 —
228 YLWang 63 — — — — — 63
228 AnandOza 63 36 — — — — 27
232 jonathanirvings 62 — — — — 62 —
232 jcvb 62 62 — — — — —
232 IZONE 62 — 62 — — — —
235 AlexLuchianov 60 — 60 — — — —
235 20I6wudi 60 — — — — 60 —
235 saketh 60 60 — — — — —
238 Monogon 58 — 58 — — — —
238 peltorator 58 58 — — — — —
240 PolarFlea 56 — — — — 56 —
240 tfg 56 — — — 56 — —
240 Quirrel 56 — 56 — — — —
243 balbit 54 — — — — — 54
243 Pa.Nic 54 — 54 — — — —
243 NeoOrgano 54 — — — 54 — —
246 alireza_kaviani 52 — — — 52 — —
246 lzoi.win 52 — — — — — 52
248 s_r_f 50 — 50 — — — —
248 icypiggy 50 — — — — 50 —
250 _Ash__ 48 — 48 — — — —
250 Shibuyap 48 48 — — — — —
252 mshcherba 46 — 46 — — — —
252 Barichek 46 — — — 46 — —
252 yspm 46 — — — — 46 —
252 PuRpLe_FoReVeR 46 46 — — — — —
252 maspy 46 — — — — — 46
257 wifiiii 45 — — — 45 — —
257 GaryZ005 45 — — — 45 — —
257 LMOliver 45 — — — — 45 —
257 physics0523 45 — — — — — 45
261 zhangzy 43 — 43 — — — —
261 suyiheng 43 — — — — — 43
261 xuanyi 43 43 — — — — —
261 arvindf232 43 — — — — 43 —
265 MofK 42 — — — — 26 16
266 lucaperju 41 — — — 41 — —
266 jiangIy 41 — — 41 — — —
266 doped.silicon 41 41 — — — — —
266 shennong 41 — — — 41 — —
270 shb 39 — — — — 39 —
270 kostia244 39 — — — — — 39
270 JettyOller 39 — — 39 — — —
273 cheissmart 37 — — — 37 — —
273 stevenkplus 37 — — 37 — — —
275 Wailydest 36 — — — — — 36
275 leaf1415 36 — 36 — — — —
275 klimoza 36 — — — 36 — —
278 Iscream2001 34 — 34 — — — —
279 Bellalabella 32 32 — — — — —
279 soltanmv 32 — 32 — — — —
279 olmrgcsi 32 — — 32 — — —
279 Sung.An 32 — — — — 32 —
283 SamBankman-Fried 31 — 31 — — — —
283 Mandy-Sa 31 — — — 31 — —
283 FluffyT 31 31 — — — — —
283 MonkeyKing 31 — — — — — 31
287 Nyaan 29 — — 29 — — —
287 amnesiac_dusk 29 29 — — — — —
287 Marckess 29 — 29 — — — —
290 dragonslayerintraining 27 27 — — — — —
290 budalnik 27 — — — — 27 —
292 catupper 26 26 — — — — —
292 Tlatoani 26 — 26 — — — —
294 A-SOUL_Bella 24 — — — — — 24
294 KeNaj712 24 — — 24 — — —
294 sstrong 24 — — — 24 — —
294 Zayin 24 24 — — — — —
298 hexagonwarrior 22 — — — — — 22
298 16silver 22 — — — — 22 —
300 sava-cska 21 21 — — — — —
300 sugarrr 21 — — 14 — — 7
300 sd0061 21 — 21 — — — —
300 loveye 21 — — — — — 21
300 yuto1115 21 — — — 21 — —
305 w0nsh 19 19 — — — — —
305 rniya 19 — — — 19 — —
305 S2speed 19 — — — — 19 —
305 almogwald 19 — 19 — — — —
309 The_Noble_Brahman_Bison 17 — — — — — 17
309 HoshimiOWO 17 17 — — — — —
309 xay5421 17 — — — 17 — —
312 C137 16 16 — — — — —
312 VladProg 16 — — — 16 — —
314 CXY007 14 — — — — — 14
314 Nero 14 — 14 — — — —
314 dendi239 14 14 — — — — —
314 cuom1999 14 — — — 14 — —
318 olphe 13 — — — 13 — —
318 destination 13 — 13 — — — —
318 eecs 13 — — — — — 13
318 SW2000 13 13 — — — — —
318 PaiGuGou 13 — — — — 13 —
323 Akulyat 12 — — 7 5 — —
324 Guoyh 11 — — — — — 11
324 Yukikaze_ 11 — 11 — — — —
324 wiwitrifai 11 11 — — — — —
324 JeanBombeur 11 — — — 11 — —
324 Atreus 11 — — 11 — — —
329 Obsidian 10 — — 10 — — —
329 Laurie 10 — — — — 10 —
329 al3xstr33t 10 — 10 — — — —
329 xwp 10 — — — — — 10
333 Ali.Kh 8 — — 8 — — —
333 nweeks 8 — — — 8 — —
333 magga 8 8 — — — — —
333 Kostroma 8 — — — — 8 —
337 Andycipation 7 7 — — — — —
337 Nots0fast 7 — — — 7 — —
337 zyb 7 — 7 — — — —
340 NoLongerRed 5 — — 5 — — —
340 kamer 5 — — — — 5 —
340 craborac 5 5 — — — — —
343 TheScrasse 4 — — — — 4 —
343 tin-jyu 4 4 — — — — —
343 strongerthanspeed 4 — — — 4 — —
346 iaNTU 3 — — 1 — 2 —
347 dfcmd 2 — — — 2 — —
347 caoyue 2 — — — — — 2
349 Jlytxdy 1 1 — — — — —
349 Werner_Yin 1 — — — — — 1
349 GRT_2018 1 — — — 1 — —

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About Unrated Educational Codeforces Round 121
By MikeMirzayanov, 2 years ago, In English

Hello, Codeforces.

Unfortunately, we have to declare the round unrated.

Absolutely, these are not issues of the side of Codeforces code, but rather it is a hardware issue. Probably, electricity, power unit or something else. This led to unexpected repeated reboots of the server with the database. I hope that we will be able to quickly deal with this.

We apologize to the writers of the round and its participants.

P.S. Please, do not downvote the round announcement: the writers are not to blame for what happened. And in general, this time it is difficult to blame someone. Sometimes hardware fails.

Mike.

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I am Mike Mirzayanov. AMA!
By MikeMirzayanov, 2 years ago, In English

But why not!

Many people here seem to know me. Or maybe not quite? I am ready to answer your questions. Ask me anything! I plan to spend no more than 3 hours on answers. Sorry if I can't answer all the questions.

Let's more or less follow the rules from here https://www.reddit.com/r/IAmA/wiki/index

Below is actually a quote from the rules.

The interviewee begins the process by starting a post, describing who they are and what they do. Then commenters from across the internet leave questions and can vote on other questions according to which they would like to see answered.

The interviewee can go through and reply to the questions they find interesting and easily see those questions the internet is dying to have the answer to.

Because the internet is asking the questions, they're going to be a mix of serious and lighthearted, and you'll find yourself sharing all kinds of things you won't find in a normal interview.

Comments will be removed under a few circumstances:

  • Abusive or harassing comments.
  • Requests for personal favors from the OP (For example, "OP, can you send me a signed autograph").
  • Top-level comments must ask a question.
  • Comments where there would be no possibility of a real answer, especially where it is deliberately creepy or offensive.
  • "I bet OP won't answer this"-type responses, which usually come after the OP has finished responding to questions.
  • "Fluff," non-contributing responses from users, responding to all of the OP's comments for karma/attention.
  • Repeatedly asking the same question.

Please, don't attempt to bypass the rules by adding a ? to a nonquestion.

Questions must be directed toward the individual(s) doing the IAMA.

Under our policies, astroturfing is the practice of an individual or group of individuals who plant questions in an IAmA post for a particular purpose. This kind of behavior is forbidden.

UPD 1: Oh, I'm kind of tired of doing this. Please keep asking questions. Tomorrow I will answer again. Don't forget to vote for the most interesting ones. I will not have time to answer everything, I will choose something. Thanks!

UPD 2:

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Top 50 Voted Blog Posts in 2021
By MikeMirzayanov, 2 years ago, In English

Hi.

Here is the list of top-voted blog posts in 2021. Find something interesting for yourself?

# Post Votes Author
1 The Ultimate Topic List (with Resources, Problems and Templates) 4383 YouKn0wWho
2 Codeforces Round #752 3156 YouKn0wWho
3 User activity in the profile! [new, Feb. 2021] 3055 geranazavr555
4 Codeforces Round #712 2866 Monogon
5 Codeforces Round #733 (Div. 1 + Div. 2) 2795 tourist
6 Codeforces Round #735 (Div. 2) 2167 YouKn0wWho
7 Things I don't know 1965 Um_nik
8 My opinion on how to practice competitive programming 1899 Radewoosh
9 Goodbye 2021. Hello 2022! 1849 MikeMirzayanov
10 Corruption, Cheating at ICPC Yinchuan 1685 NXIST_buster
11 Codeforces Global Round 14 1595 FieryPhoenix
12 Evidence of ACPC Corruption 1547 ACPC_Corruption
13 C++20 Is Released 1524 MikeMirzayanov
14 Codeforces Round #743 Is Unrated: Investigating the Reason 1522 MikeMirzayanov
15 I compiled a list of almost all useful blogs ever published on Codeforces [update: till 09.06.2021] 1500 parveen1981
16 New Year Gift: Codeforces Catalog — Early Access 1448 MikeMirzayanov
17 Codeforces: Results of 2020 [list some changes and improvements] 1394 MikeMirzayanov
18 Codeforces Round #715 1371 Kuroni
19 Giving negative feedback to contests in comments 1347 antontrygubO_o
20 (The Ultimate) Code Library 1334 YouKn0wWho
21 Where are my pants 1323 sus
22 Codeforces Round #736 1253 Agnimandur
23 On Problems vs. Questions in Competitive Programming: My solution 1178 Ari
24 Competitive Programming Hall of Fame — cphof.org 1176 Ra16bit
25 Codeforces Round #732 1175 AquaMoon
26 Codeforces Round #722 1145 AmShZ
27 Codeforces Global Round 13 1092 star_xingchen_c
28 Polygon Updates (June — August 2021) 1013 unreal.eugene
29 Codeforces Round #742 (Div. 2) 967 ScarletS
30 Codeforces Round #741. How contest author is entertaining. 950 Wind_Eagle
31 Codeforces Round #723 (Rated for Div 2) 923 errorgorn
32 Petition to make (onsite part of) ICPC WF 2020 1-computer 914 Um_nik
33 Cheater Report in Global Round 15 910 kostka
34 Codeforces Round #703 (Div. 2) 908 okwedook
35 Codeforces Round #743 878 Markadiusz
36 Why didn't anyone tell me that Petr was in the Vatican? 872 mcqueencin
37 [Tutorial] GCC Optimization Pragmas 854 nor
38 See your Codeforces 2021 Journey!! 830 abdude824
39 Discussion: Modern G++ Command Line 830 MikeMirzayanov
40 Codeforces Global Round 15 823 dario2994
41 China team won the IOI2021 820 Fuyuki
42 Codeforces Round #698 (Div.1, Div.2) 816 Nezzar
43 Codeforces Round #746 (Div. 2) 806 Hemose
44 Codeforces Round #754 (Div. 2) 805 JeevanJyot
45 Codeforces Round #745 Editorial 799 interlude
46 VK Cup 2021 — Final (Engine) and Codeforces Round #740 798 tourist
47 Codeforces Round #738 (Div. 2) 796 Bazoka13
48 Codeforces Round #708 781 shishyando
49 April Fools Day Contest 2021 781 Nickolas
50 Codeforces Round #761 (Div. 2) 773 snowysecret

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New Year Gift: Codeforces Catalog — Early Access
By MikeMirzayanov, 2 years ago, In English

Hey!

Are you celebrating the New Year already? I wish you a Happy New Year. I wish you progress, joy and health.

We decided to show the current progress in the catalog of significant Codeforces posts.

So far, quite a bit has been implemented, but somehow you can already use it! Would you like to see it? Follow the link:



As planned, the catalog will collect and classify interesting and useful posts from Codeforces. Indeed, many useful articles have been written in Codeforces over 12 years (God, already 12 years!).

The catalog will be a kind of Codeforces golden fund in the future.

The catalog is a tree of topics to which posts can be added. We will still work on its functionality, for now there are only basic features. Don't be discouraged if something is not supported, which is very necessary — just let me know!

Any red user can enable directory editing. Remember that it is extremely important to make all changes thoughtfully and carefully. The tree should not become infinite in size. You need to have a sense of proportion when detailing topics. Please add only good, useful articles to the directory. If there is a disagreement on the contents of the catalog, the administration will make the final decision.

Hope this will be helpful. And together we can put together a catalog and keep the catalog up to date.

P.S. Many thanks to KAN who helped a lot with suggestions and catalog initial content.

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Likes in Posts and Comments
By MikeMirzayanov, 2 years ago, In English

Hello.

Here's a small improvement for posts and comments. Likes can now be specified in their markup. Maybe this will be useful for organizing some kind of polls or collecting feedback.

Here are some examples:

Markup
Use square brackets instead of round 		Result
Simple likes widget
(likes:1)
Same keys means same likes widgets
(likes:2)
(likes:2)
Same keys and different groups can be used for exclusive choices
(likes:3,option1)
(likes:3,option2)

Yes, I know that this feature can be improved. I would prefer that we try to use it a little and understand what exactly is missing the most. Maybe we need to implement the fully functional polls.

Let's do a small survey using the new feature.

  1. What is your age range?

    • under 16:
    • 16-20:
    • 21-25:
    • 26-35:
    • 36+:

  2. Tabs or spaces?

    • tabs:
    • spaces:

  3. Have you had covid??

    • yes:
    • no:
    • I don't know:

  4. Lately, there have been a lot of meaningless blogs on Codeforces. Is it worth strengthening measures to fight against them?

    • yes definitely:
    • rather yes, but not necessarily:
    • rather no, I read some of them:
    • no definitely:

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Goodbye 2021. Hello 2022!
By MikeMirzayanov, 2 years ago, In English

Hello Codeforces!

Oh yes, 2021 ends! I recently realized that 2022 is pronounced like "2020 too". Not that. I want a completely different year!

Anyway, we did a nice job this year. I hope we have pleased you with interesting problems. Thanks to the round coordinators and writers! You make our community richer. Please make us happy in 2022!

I wish you all interesting tasks and brilliant solutions! I wish you error-free code and wish us only rated rounds :-)

Hello, 2022!

And we have traditional gifts!

Change Handle Feature

Hurry! Only until the 10th of January, you can change your handle (but only once)! Note that it will be possible to roll back the changes or change the handle again only after a year. Be careful what you wish for.

You can change your handle to the new one which wasn't used before by anybody or which was used by you before. The links to a profile page with an old handle would automatically redirect to the actual profile.

Again, this year if you took part in at least 10 rounds you can request a handle of an inactive participant. It means that the participant should have a period of activity on Codeforces of at most 180 days, this period should be in 2019 or earlier. The inactive participant can't have posted comments, messages, and so on. It can't take part in more than 2 contests. It will be automatically renamed and informed by email. A user has the opportunity to request back his/her handle: in this case, we will roll back the change and return your previous handle to you. If you can't change your handle to another, it means that some requirements don't meet. Please do not ask me to do something with it. Especially, I do not like requests like "this is my second account, I took an interesting handle myself". I'm not Santa Claus.

Talking about handles I always
reminisce the following story. Once a user wrote me the message: "Please change my handle from I_love_Valya to I_love_Sveta, as I no longer love Valya ..."

New Year's Masquerade of Colors and Ranks

The traditional magical tab has appeared in the profile setting. Happy New Year!

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Codeforces Global Rounds 2021: Current Results (GR13-GR17)
By MikeMirzayanov, 2 years ago, In English

In 2021 (as in 2019 and 2020), with the support of XTX Markets, 6 rounds of the new Codeforces Global Rounds are held: common rounds for both divisions of 7–9 problems each. The duration of the rounds is 2-3 hours, depending on the number and complexity of the problems. All such rounds are rated for all participants. At each such round, 50 brand T-shirts are handed out, and we are happy to give T-shirts to all problem authors.

The prizes for the 6-round series in 2021:

  • In each round top-100 participants get points according to the table.
  • The final result for each participant is equal to the sum of points he gets in the five rounds he placed the highest.
  • The best 20 participants over all series get sweatshirts and place certificates.

Current standings after five rounds (sorted by total points in four best placed rounds):

Place Contestant = GR 13 GR 14 GR 15 GR 16 GR 17
1 Radewoosh 3291 291 1000 — 1000 1000
2 tourist 2815 135 403 1000 706 706
3 ksun48 2201 135 706 706 443 346
4 maroonrk 1717 1000 226 142 226 265
5 Petr 1647 575 — 497 — 575
6 jiangly 1501 497 346 63 497 161
7 Benq 1418 — 497 575 346 —
8 Um_nik 1199 176 575 346 102 34
9 duality 1045 277 371 186 211 —
10 gop2024 1006 706 — 176 70 54
11 Golovanov399 994 254 277 138 — 325
12 aid 868 226 145 218 198 226
13 tatyam 806 — 291 161 325 29
14 lumibons 766 325 — 265 — 176
15 sunset 742 371 — 371 — —
16 dlalswp25 707 204 161 — 131 211
17 Subconscious 699 — — 171 125 403
18 gisp_zjz 688 — 153 198 60 277
19 hitonanode 657 — 181 62 307 107
20 never_giveup 626 218 192 74 — 142
21 244mhq 625 — 218 291 116 —
22 LayCurse 622 149 265 192 — 16
23 Ormlis 603 — 171 48 235 149
24 QAQAutoMaton 575 — — — 575 —
25 natsugiri 574 — 166 110 80 218
26 hos.lyric 563 128 — 254 — 181
27 mango_lassi 555 119 135 97 204 11
28 kotatsugame 531 — 149 105 277 —
29 LJC00118 523 198 325 — — —
29 dreamoon_love_AA 523 — 52 307 72 92
31 Maksim1744 517 54 244 66 153 —
32 VivaciousAubergine 515 — 72 443 — —
33 yhx-12243 511 — 443 68 — —
34 He_Ren 502 — — — 371 131
35 he_____hezhou 497 — — — — 497
36 SpyCheese 489 — — 46 — 443
36 snuke 489 — — 27 218 244
38 AndreySergunin 444 244 78 122 — —
39 RALZH 443 443 — — — —
40 nuip 427 — — 166 90 171
41 Toxel 420 90 — 76 — 254
42 NotaMotuaQAQ 417 110 307 — — —
43 TadijaSebez 408 — 5 403 — —
44 Alice_foo_foo 403 — — — 403 —
44 qazswedx2 403 403 — — — —
46 Farhod 397 153 102 — 142 —
47 Endagorion 395 211 1 17 — 166
48 ecnerwala 391 346 — 45 — —
49 hanbyeol_ 390 — — — 291 99
50 blackbori 377 — 83 50 244 —
51 SSRS_ 375 68 90 31 — 186
52 huyinghao0706 371 — — — — 371
53 sansen 370 — — 116 254 —
54 Sugar_fan 351 235 116 — — —
55 tmwilliamlin168 348 — 41 — — 307
56 turmax 339 — 142 119 78 —
57 ko_osaga 325 — — 325 — —
58 p_b_p_b 307 307 — — — —
58 353cerega 307 52 — 153 — 102
60 Marcin_smu 301 265 — — — 36
61 receed 300 102 198 — — —
62 hank55663 298 — — — 63 235
63 Froggygua 291 — — — — 291
64 fanache99 288 — 131 — 105 52
65 Isonan 281 107 157 — — 17
66 dario2994 280 94 128 — 58 —
67 KostasKostil 277 — — 277 — —
68 jiangly_fan 273 — — 157 116 —
69 Rafbill 272 80 — — 87 105
70 ugly2333 266 — 138 54 — 74
71 fivedemands 265 — — — 265 —
72 Temotoloraia 257 — — 226 10 21
73 Elegia 254 — 254 — — —
74 heno239 246 — 176 70 — —
75 Egor 244 — — 244 — —
75 AliShahali1382 244 85 24 135 — —
77 l1ll5 238 34 — — — 204
78 kotamanegi 235 — — 235 — —
78 _h_ 235 — 235 — — —
80 dorijanlendvaj 228 10 — 52 166 —
81 noimi 225 — 94 34 97 —
82 TLEwpdus 213 — 2 211 — —
83 ehnryx 211 — 211 — — —
84 nocriz 204 — 204 — — —
84 renascencepjw0510 204 — — 204 — —
86 fastmath 202 92 110 — — —
86 amethyst0 202 181 — 21 — —
88 inaFSTream 198 — — — — 198
89 atomicenergy 197 46 16 — — 135
90 uwi 192 192 — — — —
90 Worteltje 192 — — — — 192
90 Rewinding 192 — — — 192 —
93 Geothermal 188 — — — 157 31
94 Argentina 186 — — — 186 —
94 nantf 186 — 186 — — —
94 YeongTree 186 186 — — — —
97 voidmax 181 — — — 181 —
97 scott_wu 181 — — 181 — —
99 Torta 177 — — 80 — 97
100 nick452 176 — — — 176 —
101 fedoseev.timofey 174 39 63 72 — —
102 cnoi 171 — — — 171 —
102 MAOooOAM 171 171 — — — —
104 nutella_waxberry 166 166 — — — —
105 kmjp 165 — — 22 27 116
106 Nachia 164 138 — 26 — —
107 Anadi 161 161 — — — —
107 huhaoo 161 — — — 161 —
109 Ra16bit 158 66 — — 92 —
110 dsgrekova2 157 157 — — — —
110 peti1234 157 — 125 — 32 —
110 zh0ukangyang 157 — — — — 157
113 tute7627 155 — 27 58 — 70
114 AutumnKite 153 — — — — 153
115 Egor.Lifar 152 — 8 16 128 —
116 isaf27 150 63 — 87 — —
117 Swistakk 149 — — 149 — —
117 TLE 149 — — — 149 —
119 Amoo_Safar 145 — — 145 — —
119 ShuijunDainifei 145 — — — — 145
119 mnaeraxr 145 145 — — — —
119 137_345_2814 145 — — — 145 —
123 saba2000 144 125 — 19 — —
124 ppavic 142 142 — — — —
125 m_99 141 22 — — 119 —
126 Xellos 140 — 92 — 48 —
127 mtsd 138 — — — — 138
127 why_no_girlfriend 138 — — — 138 —
129 crackersamdjam 135 — — — 135 —
129 conqueror_of_tourist 135 50 37 — — 48
131 flashmt 131 — — 94 — 37
131 shb123 131 — — 131 — —
133 qwerty787788 128 — — 128 — —
133 Zhtluo 128 — — — — 128
135 Noam13 126 2 — 2 122 —
136 Melania 125 — — — — 125
136 abc864197532 125 — — 125 — —
138 AlesyaIvanova 124 — 74 — 50 —
139 Arayi 122 122 — — — —
139 Hazyknight 122 — 122 — — —
139 djq_cpp 122 — — — — 122
142 errorgorn 121 — — 43 — 78
143 krijgertje 119 — 119 — — —
143 ainta 119 — — — — 119
145 potato167 117 — — 37 22 58
146 eatmore 116 116 — — — —
146 Merkurev 116 — — — 116 —
148 simonlindholm 113 — — 113 — —
148 Alan233 113 — — — — 113
148 Yongaron 113 — 113 — — —
148 chenyanbo 113 113 — — — —
152 Karry5307_AK_NOI2024 110 — — — — 110
153 Pyqe 108 — 45 — 63 —
154 Itst_boyfriend 107 — — 107 — —
154 Tiramister 107 — 107 — — —
154 asdsasd 107 — — — 107 —
157 Wu_Ren 105 105 — — — —
157 ix35 105 — 105 — — —
159 Alex_2oo8 102 — — 102 — —
160 antontrygubO_o 99 — 99 — — —
160 krismaz 99 — — 99 — —
160 tabr 99 — — — 99 —
160 Comet_Honeymoon 99 99 — — — —
164 oleh1421 98 — 4 — 94 —
165 donentseto 97 97 — — — —
165 Suika_predator 97 — 97 — — —
167 BurnedChicken 96 — — 60 29 7
168 dengyaotriangle 94 — — — — 94
169 Kodaman 92 — — 92 — —
170 LiciaDu 90 — — 90 — —
170 ljcleo 90 — — — — 90
170 TeaPot 90 76 — 14 — —
173 Aishiteru. 87 87 — — — —
173 Enchom 87 — 87 — — —
173 antekb 87 — — — — 87
176 God_Of_Blunder 85 — — — 85 —
176 voover 85 — — 85 — —
176 sumitacchan 85 — 85 — — —
176 Morollcinna 85 — — — — 85
180 szhlg 83 83 — — — —
180 skywalkert 83 — — 83 — —
180 PubabaOnO 83 — — — — 83
180 ezLadder 83 — — — 83 —
184 djq_fpc 80 — 80 — — —
184 Roundgod 80 — — — — 80
186 SirShokoladina 78 78 — — — —
186 scli_weapon 78 — — 78 — —
188 C.S.T.T 76 — — — 76 —
188 AoLiGei 76 — — — 76 —
188 orzdevinwang 76 — 76 — — —
188 dXqwq 76 — — — — 76
192 prick 74 74 — — — —
192 Savior-of-Cross 74 — 17 56 — 1
194 szb 72 72 — — — —
194 KevinWan 72 — — — — 72
196 zscoder 71 37 — — 34 —
197 hamlet 70 70 — — — —
197 timmyfeng 70 — 70 — — —
199 happyguy656 68 — — — — 68
199 veckoper 68 — 68 — — —
199 Izumi_Chiaki 68 — — — 68 —
202 kektus 66 — 66 — — —
202 awoo 66 — — — 66 —
202 K_T_O 66 — — — — 66
205 Rubikun 63 — 39 — — 24
205 Kalptaru 63 — — — — 63
207 jonathanirvings 62 — — — — 62
207 jcvb 62 62 — — — —
207 IZONE 62 — 62 — — —
210 20I6wudi 60 — — — — 60
210 AlexLuchianov 60 — 60 — — —
210 saketh 60 60 — — — —
213 risujiroh 58 58 — — — —
213 Monogon 58 — 58 — — —
213 peltorator 58 58 — — — —
216 PolarFlea 56 — — — — 56
216 tfg 56 — — — 56 —
216 Quirrel 56 — 56 — — —
219 Pa.Nic 54 — 54 — — —
219 NeoOrgano 54 — — — 54 —
221 alireza_kaviani 52 — — — 52 —
222 s_r_f 50 — 50 — — —
222 icypiggy 50 — — — — 50
224 _Ash__ 48 — 48 — — —
224 Shibuyap 48 48 — — — —
226 mshcherba 46 — 46 — — —
226 Barichek 46 — — — 46 —
226 yspm 46 — — — — 46
226 PuRpLe_FoReVeR 46 46 — — — —
230 wifiiii 45 — — — 45 —
230 GaryZ005 45 — — — 45 —
230 LMOliver 45 — — — — 45
233 zhangzy 43 — 43 — — —
233 xuanyi 43 43 — — — —
233 arvindf232 43 — — — — 43
236 lucaperju 41 — — — 41 —
236 jiangIy 41 — — 41 — —
236 Vercingetorix 41 — — — — 41
236 doped.silicon 41 41 — — — —
236 shennong 41 — — — 41 —
241 shb 39 — — — — 39
241 JettyOller 39 — — 39 — —
243 cheissmart 37 — — — 37 —
243 stevenkplus 37 — — 37 — —
245 leaf1415 36 — 36 — — —
245 AnandOza 36 36 — — — —
245 klimoza 36 — — — 36 —
248 Iscream2001 34 — 34 — — —
249 Bellalabella 32 32 — — — —
249 olmrgcsi 32 — — 32 — —
249 soltanmv 32 — 32 — — —
249 Sung.An 32 — — — — 32
253 Mandy-Sa 31 — — — 31 —
253 SamBankman-Fried 31 — 31 — — —
253 FluffyT 31 31 — — — —
256 Nyaan 29 — — 29 — —
256 amnesiac_dusk 29 29 — — — —
256 Marckess 29 — 29 — — —
259 dragonslayerintraining 27 27 — — — —
259 budalnik 27 — — — — 27
261 wasa855 26 — — — 26 —
261 catupper 26 26 — — — —
261 Tlatoani 26 — 26 — — —
261 MofK 26 — — — — 26
265 KeNaj712 24 — — 24 — —
265 sstrong 24 — — — 24 —
265 Zayin 24 24 — — — —
268 Konijntje 22 — 22 — — —
268 16silver 22 — — — — 22
270 sava-cska 21 21 — — — —
270 sd0061 21 — 21 — — —
270 yuto1115 21 — — — 21 —
273 w0nsh 19 19 — — — —
273 rniya 19 — — — 19 —
273 S2speed 19 — — — — 19
273 almogwald 19 — 19 — — —
277 yosupo 18 — — 4 — 14
278 HoshimiOWO 17 17 — — — —
278 xay5421 17 — — — 17 —
280 C137 16 16 — — — —
280 VladProg 16 — — — 16 —
282 Nero 14 — 14 — — —
282 sugarrr 14 — — 14 — —
282 dendi239 14 14 — — — —
282 cuom1999 14 — — — 14 —
286 olphe 13 — — — 13 —
286 SW2000 13 13 — — — —
286 PaiGuGou 13 — — — — 13
286 destination 13 — 13 — — —
290 Akulyat 12 — — 7 5 —
291 Yukikaze_ 11 — 11 — — —
291 wiwitrifai 11 11 — — — —
291 JeanBombeur 11 — — — 11 —
291 Atreus 11 — — 11 — —
295 Obsidian 10 — — 10 — —
295 Laurie 10 — — — — 10
295 al3xstr33t 10 — 10 — — —
298 Ali.Kh 8 — — 8 — —
298 nweeks 8 — — — 8 —
298 Kostroma 8 — — — — 8
298 magga 8 8 — — — —
302 Nots0fast 7 — — — 7 —
302 zyb 7 — 7 — — —
302 Andycipation 7 7 — — — —
305 NoLongerRed 5 — — 5 — —
305 kamer 5 — — — — 5
305 craborac 5 5 — — — —
308 TheScrasse 4 — — — — 4
308 tin-jyu 4 4 — — — —
308 strongerthanspeed 4 — — — 4 —
311 iaNTU 3 — — 1 — 2
312 dfcmd 2 — — — 2 —
313 Jlytxdy 1 1 — — — —
313 GRT_2018 1 — — — 1 —

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C++20 Is Released
By MikeMirzayanov, 2 years ago, In English

Hello, Codeforces.

Please, welcome c++20 support on Codeforces. Yes, it is 64-bit. Thanks to Brecht Sanders: I used his distribution GCC-11.2.0-64 from https://winlibs.com/.

If you have installed PBOX, you can add this compiler with the line pbox install gcc11-64-winlibs. Probably, a good idea is to add C:\Programs\gcc11-64-winlibs\bin into the PATH. More about PBOX you can read here.

I use the compilation command line similar to other GCC installations: g++ -Wall -Wextra -Wconversion -static -DONLINE_JUDGE -Wl,--stack=268435456 -O2 -std=c++20 <source>. The only differences are -std=c++20 and -Wall -Wextra -Wconversion (I plan to use somehow such warnings in Polygon to suggest fixes in uploaded files).

Now you can use c++20 in your solutions. I'm not sure there are many features useful in competitive programming. Probably, I'm wrong. For example, now you can write vector v{vector{1, 2}}; instead of vector<vector<int>> v{vector<int>{1, 2}};. What else is useful? Please, if you are good with modern C++ then write.

You might be interested in looking at such a table. Before implementation, I always test every C++ distribution for the efficiency of reading and writing large amounts of data. For example, the latest GCC compiler from MSYS2 is terribly slow in some cases. I don't want to use it here. Also, it happens that some specifiers like lld or Lf work unexpectedly. In the table by reference, the second line is the added compiler. The columns correspond to different tests. The cell contains the time of the test execution. If I have time, I will someday publish scripts for testing c++ compiler installations.

Bye for now,
— Mike

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PyPy 3-64 Is Released
By MikeMirzayanov, 3 years ago, In English

Hey! I'm happy to report that Pypy3 is supported. Please test that it works as expected. Thanks!

P.S. I remember about GCC 11, it is in the progress. See you soon.

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Codeforces Round #743 Is Unrated: Investigating the Reason
By MikeMirzayanov, 3 years ago, In English

Hello.

Sorry for it. Actually, right now I don't have any idea why testing is so slow now. Obviously, it doesn't work as expected. It is not because of problems. So please don't blame writers or coordinators. I'm investigating the reason, but don't see it now.

I myself am very upset and I apologize to the authors, coordinator, and participants. I will do my best to find the cause and fix it. Surprisingly, we haven't made any big changes to this part of the system lately. But something went wrong.

Mike.

UPD: https://codeforces.com/blog/entry/95081#comment-841873

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Discussion: Modern G++ Command Line
By MikeMirzayanov, 3 years ago, In English

Hello Codeforces!

I am in the process of making improvements and updates to the judgment machines. I've read the post https://codeforces.com/blog/entry/94587 and I think, maybe it is a good idea to make such a compilation line -O3 -funroll-loops -march=native -mtune=native? I haven't done any research that it is definitely better than -O2 and it is best in the general case for CP solutions. In a way, this will only strengthen the gap from Python/PyPy/Java, on the other hand: in pragmas and so you can set up everything. What do you think? What are suggestions to the command line?

P.S. You got it right. Yes, gcc11 std=c++20, pypy3 64-bit and more are coming.

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Maintenance works on Round 739. Don't be surprised.
By MikeMirzayanov, 3 years ago, In English

Hello, Codeforces.

We want to run a series of load testing in the production environment for running contests. For this reason, Codeforces Round 739 will be temporarily extended (in order to test it at the current round). We will temporarily disable the ability to send solutions to it so that its extended duration will not affect the results. After the completion of the work, the duration of the round will be returned.

Our current plan is to finish today.

Mike

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Google Code Jam 2021: Round 2
By MikeMirzayanov, 3 years ago, In English

Hey!

As I don't see the post discussing the round, I decided to write this.

I do not participate much in contests now. But I love Code Jam. Thanks to problem writers and organizers!

It seemed to me that this round was no more difficult than the previous one. How do you like it?

I liked the problems:

  • A (tags: interactive, constructive): strange problem — the most naive approach fits into the requirements on the total cost of requests;
  • B (tags: number theory, dp): I wrote some kind of DP with memorization of $$$(a, s)$$$, where $$$a$$$ is the last element in the sequence we already placed (I build in increasing order) and $$$s$$$ is the total sum for the future elements. I don't have a proof why it works fast, probably because of the number of divisors is small.
  • C (tags: combinatorics, recurrence): the last occurrence of 1 is the position of $$$n$$$, so we can divide sequence with this position on two parts and use DP to calculate the answer (don't forget to multiply on binomial coefficient);
  • D (tags: graphs, flows, greedy): I used min-cost-flow to match Ms on the first field and the second in optimal way. I tried all possible values of flow to iterate over all possible pairs of Ms I want to match and took best cost among all choices.

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Codeforces: Results of 2020 [Annual Report]
By MikeMirzayanov, 3 years ago, In English

Hi Codeforces!

Yes, I know it's already April. Time flies so fast lately! Exactly a year ago we were just learning all the "delights" of lockdown.

So let's remember this 2020! What was it like? I don't know about you, but we had a hell of a lot of work.

I will now show you some graphs and you will be very surprised. Lockdown effect? Of course, but we did our best too.

Many thanks to everyone who did not stand aside! In 2020, we celebrated our 10th anniversary and crowdfunding money helps us grow and move forward. You helped us and each other. Thank you. Thank you for your contribution!

We've been working hard all year to make this community a better place. Did it work out? It's up to you to judge. Many thanks to everyone who invested time and effort:

Time to take stock of 2020.

Partner Events

We are pleased to hold programming competitions with companies or for companies. I'm sure this is a great way to support the community of young programmers and hire talented candidates. Here is a list of our main partners this year:

  • Telegram and personally Pavel Durov is supporting Codeforces activities for many years, every regular round is held with their help, thank you!
  • ICPC — in 2020 we held several joint events (and we liked it!), I hope there will be more
  • Mail.Ru — Technocup and Russian AI Cup
  • VK, VK Cup — now a personal multi-track competition for Russian-speaking programmers
  • XTX Markets, Codeforces Global Rounds — a series of 6 rounds with a separate scoring and souvenirs for the best participants
  • Harbour.Space University — a series of educational rounds, the selection of summer school Tech Scouts
  • JetBrains, Kotlin Heroes Rounds — Kotlin programming language contests
  • Huawei — research competitions (marathons) with elements of machine learning
  • Raiffeisenbank — round for both divisions with cool prizes
  • Grakn Labs — round for both divisions with money prizes
  • Microsoft, Microsoft Q # Coding Contest — unusual quantum computing competition

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Codeforces: Results of 2020 [list some changes and improvements]
By MikeMirzayanov, 3 years ago, In English

Hello, Codeforces!

I understand that 2021 has been going on for a long time, but here I have picked up a subset of some of the improvements that the Codeforces team made in 2020. Soon I will publish numbers (no, charts) with statistics for 2020. In the meantime, I bring to your attention a list of changes and improvements.

By the way, this is a decent list. This is about half to a quarter of all changes. It's just that other changes are more often somewhere in the internals of the system and are not visible to users. Please read this list. Each item is the effort of someone from the team. Thanks to geranazavr555, kuviman and cannor147 for their efforts. You've made our platform better! Well, by the way, I don't quit programming and many improvements were made by me.

The items on the list are written in a concise and informal form, many of the items I just copied from commit messages from git. If you want more details — ask in the comments, we will tell you! Of course, I forgot to include some improvements in the list.

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Goodbye 2020. Hello 2021!
By MikeMirzayanov, 3 years ago, In English

Hello Codeforces!

This unusual and difficult 2020 has come to an end! What will the new year be like? I wish all of us that we have the opportunity to meet in person so that the contests take place not only online. I ask you to think of something important and good. Let this wish come true!

We have had a large number of rounds this year. I hope we have pleased you with interesting problems. Thanks to the round coordinators and writers! You make our community richer. Please make us happy in 2021!

I wish the participants victories over yourself (and over problems!) and development of your skills, interest and curiosity!

Hello, 2021!

And we have traditional gifts!

Change Handle Feature

Hurry! Only until the 10th of January, you can change your handle (but only once)! Note that it will be possible to roll back the changes or change the handle again only after a year. Be careful what you wish for.

You can change your handle to the new one which wasn't used before by anybody or which was used by you before. The links to a profile page with an old handle would automatically redirect to the actual profile.

Again, this year if you took part in at least 10 rounds you can request a handle of an inactive participant. It means that the participant should have a period of activity on Codeforces of at most 180 days, this period should be in 2017 or earlier. The inactive participant can't have posted comments, messages and so on. It can't take part in more than 2 contests. It will be automatically renamed and informed by email. A user has the opportunity to request back his/her handle: in this case, we will roll back the change and return your previous handle to you. If you can't change your handle to another, it means that some requirement doesn't meet. Please do not ask me to do something with it. Especially, I do not like requests like "this is my second account, I took an interesting handle myself". I'm not Santa Claus.

Talking about handles I always
reminisce the following story. Once a user wrote me the message: "Please change my handle from I_love_Valya to I_love_Sveta, as I no longer love Valya ..."

New Year's Masquerade of Colors and Ranks

The traditional magical tab has appeared in the profile setting. Happy New Year!

— MikeMirzayanov

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