Best known Regex Golf solutions (SPOILERS) - Classic level set - (SPOILERS)

gistfile1.md

Collected solutions for Regex Golf, Classic level set

See also:
jpsim gist (discussion)
jonathanmorley gist (discussion)
teukon's Draft Regex Golf Bonus Levels
Solutions to teukon's Draft Regex Golf Bonus Levels (SPOILERS! SPOILERS!) and discussion of mathematical regexes
Continued discussion of Regex Golf Bonus Levels and mathematical regexes (SPOILERS! SPOILERS!)

Please let me know if you find any errors here, or can fill in any of the missing data.

Timestamps are in UTC. Be careful when following GitHub comment links – spoilers may be seen for other levels.

If I manage to discover solutions matching the unpublished high-score holders in length, I'm leaning towards publishing them here only as md5sums, so as not to further taint the high-score lists on Regex Golf.

There are some very wide tables below, which are uncomfortably constrained by the GitHub frameworks CSS. So I would suggest using a browser plugin to override the style with gist-wide.css.

Key to credits:

• P = Usenet: comp.lang.perl.misc
• HN = Hacker News
• R = reddit
• GH = GitHub
• RG~ = Regex Golf old high score list, no longer online (the existence of these records was not publicly known until andersk's 2014-01-07 12:27:38 post)
• RG = Regex Golf current high score list

Exact solutions (to the test cases)

Level	Length	Regex	Date	Credit
Plain strings	3	one of the below	before 2013-12-20	alok (RG~)
	3	foo	2013-12-20 11:18:54	Rhomboid (R)
		foo	2013-12-20 14:01:04	ZirconCode (HN)
		f.o	2014-01	Peter Norvig
Anchors	2	k$	before 2013-12-20	alok (RG~)
It never ends	6	u(?!.)
	3	u\b
Ranges	8	one of the below	before 2013-12-20	alok (RG~)
	8	^[a-f]*$	2013-12-20 11:18:54	Rhomboid (R)
		[a-f]{4}	2013-12-20 14:09:44	Sir_Cmpwn (HN)
		[a-g]{4}
		[a-h]{4}
		^[a-g]*$	2013-12-20 15:47:57	chingjun (HN)
		^[a-f]*$	2013-12-20 18:09:39	josephlord (HN)
		^[a-h]*$
Backrefs	9	(...).*\1	before 2013-12-20	alok (RG~)
Abba	14	^(?!(.)+\1)|ef	2013-12-26 14:37:35	sammiya (GH)
	14	one of the above or below	2014-01-07 12:27:38	cesium (RG~) (discovery date is earlier than indicated date)
	14	^(?!(.)+\1)|.u	2017-07-27 13:21:15	depperm (GH)
	14	^(?!(.)+\1)|fu
A man, a plan	13	almost certainly one of the below	before 2013-12-20	Scott (RG~)
	13	^(.)[^p].*\1$	2013-12-20 12:10:04	Bisqwit (R)
		^(.)[^p].*\1$	2013-12-20 15:43:30	hyp0 (HN)
		^(.)[^p].+\1$
	15	^(\w(?!p)).*\1$	2013-12-20 18:48:59	Athox (R) - edited 2013-12-20 20:23:59
Prime	14	^(?!(11+)\1+$)****	1997-10-22 18:17:07	Abigail (P)
	14	one of the below	before 2013-12-20	alok (RG~)
	14	^(?!(xx+)\1+$)	2013-12-20 11:18:54	Rhomboid (R)
	14	^(?!(xx+)\1+$)	2013-12-20 12:10:04	Bisqwit (R)
	14	^(?!(x+x)\1+$)
	14	^(?!(.+.)\1+$)
	14	^(?!(..+)\1+$)
	16	^(?!(..+)(\1)+$)	2013-12-20 16:14:12	josephlord (HN)
Four	11	(.)(.\1){3}	before 2013-12-20	alok (RG~)
	14	([aeio]).{5}\1	2013-12-20 11:18:54	Rhomboid (R)
	11	(.)(.\1){3}	2013-12-20 12:10:04	Bisqwit (R)
		(.)(.\1){3}	2013-12-20 13:13:38	osuushi (R)
		(.)(.\1){3}	2013-12-20 15:05:14	chrismorgan (HN)
Order	11	^[^o]?.{5}$	before 2013-12-20	andersk (RG~,GH)
	11	^.{5}[^e]?$	2013-12-20 12:10:04	Bisqwit (R)
	11	^.{5}[^e]?$	2013-12-20 16:13:09	noggin-scratcher (R)
		^.{5}[^e]?$	2013-12-20 21:50:12	ekke (HN)
		^[^o]?.{5}$	2013-12-20 22:13:14	balrok (GH)
Triples	34	[02-5][123][257]|[07][0269]+3?$|55	before 2013-12-20	andersk (RG~,GH)
	56	^(([147]4|40|3[269]|9[05]|[378]1).+|0[369]*|[81][257])*$	2013-12-20 12:10:04	Bisqwit (R)
	44	^[387][12479]|00($|[369]|1[25])|5[54]|2[437]	2013-12-21 10:05:27	grobie (GH)
	40	00($|[369]|1[25])|(^.|9|3)..5|4.2|^[38]1	2013-12-23 03:15:47	alexandrosm (GH)
	39	32|.[25][345].|00([369]|1[25]|$)|[07]2$	2013-12-23 07:10:33	rabcyr (GH)
	36	00([369]|1[25]|$)|.1.+4|3.*7.|4.2|55	2013-12-23 12:55:08	alexandrosm (GH)
	34	00($|3|6|9|12|15)|4.2|.1.+4|55|.17	2013-12-23 21:02:53	alexandrosm (GH)
Glob	17	[unpublished]	before 2013-12-20	andersk (RG~,GH)
	23	ai|c$|^p|[bcnrw][bnopr]	2013-12-21 18:37:50	nwellnhof (HN)
		[bncrw][bporn]|^p|c$|ta	2013-12-23 16:04:15	bbarry (GH) - some regexes in this comment were edited after the indicated date; may include this regex
		[bcnrw][bnopr]|^p|t[a*]	2018-12-01	Davidebyzero (GH,RG)
		[bcnrw][bnopr]|^p|en.?t	2018-12-01	Davidebyzero (GH,RG)
		[cnprw][opr]|le\w|ai|c$	2018-12-08	Davidebyzero (GH,RG)
		[cnprw][opr]|le\w|ta|c$	2018-12-08	Davidebyzero (GH,RG)
		[cnprw][opr]|le\w|t[a*]	2018-12-08	Davidebyzero (GH,RG)
		[cnprw][opr]|le\w|en.?t	2018-12-08	Davidebyzero (GH,RG)
		[^rt][cenprw][n-r][a-t]	2019-12-10 08:46:41	Davidebyzero (GH,RG)
	60	^(.*)\*(.*) .* \1.+\2$|^(.+) .* \3$|^.*\*(.*)\*.* .* .+\4.+$	2014-01-08 18:00:49	sorcio (GH)
	66	^(.*) .* \1$|^(.*)\*(.*) .* \2.+\3$|(.*)\*(.*)\*(.*) .* \4.+\5.+\6	2014-01-13 04:30:24	sshock (GH)
	54	^((\w*)( .+ \2$|\*(\w*)( .+ \2.+\4$|\*.* .+ \2.+\4.)))	2014-02-13 04:55:56	Davidebyzero (GH)
	50	^((.*)(.+ \2$|\*(.*)( .+ \2.+\4$|\*.*.+ \2.+\4.)))	2018-12-11	Davidebyzero (GH)
	22	[unpublished]	2016-11…2017-01 ≈	Gael (RG)
	22	[unpublished]	2019-12-06 12:27:55	Davidebyzero (GH, RG)
	21	[unpublished]	2018-02 ≈	LLB (RG)
Balance	24	[unpublished]	before 2013-12-20	andersk (RG~,GH)
	34	^(<(<(<(<(<(<.*>)*>)*>)*>)*>)*>)*$	2013-12-20 15:24:00	Overv (R) - edited 2013-12-20 15:56:16; it is unknown if the regex was longer before the edit
		^(<(<(<(<(<(<<>>)*>)*>)*>)*>)*>)*$	2013-12-20 16:13:39	nadinengland (HN)
	33	^(<(<(<(<(<(<.*)*>)*>)*>)*>)*>)*$	2013-12-20 18:39:40	jensweh (R)
	32	^(<(<(<(<(<>)*>|.{9})*>)*>)*>)*$	2014-01-02 22:55:11	alexandrosm (GH)
	31	^(<(<(<(<<?>?>|.{9})*>)*>)*>)*$	2014-01-05 14:04:09	alexandrosm (GH)
	28	^$|.{37}|^<(.(?!><*.>$).)*>$	2014-02-27 01:49:48	Davidebyzero (GH,RG)
	26	.{37}|^(<(..(?!<.>$))*>)*$	2014-03-23 08:47:49	Davidebyzero (GH,RG)
	22	[unpublished]	2018-10-23…2018-12≈	TH (RG)
Powers	17	one of the 17-scoring ones below	before 2013-12-20	andersk (RG~,GH)
	54	^((((((((((x)\10?)\9?)\8?)\7?)\6?)\5?)\4?)\3?)\2?)\1?$	2013-12-20 13:26:43	Iwonderifthisistaken (R)
	52	^xx?$|^((((((((x{4})\8?)\7?)\6?)\5?)\4?)\3?)\2?)\1?$	2013-12-20 15:07:07	Hrafnahnef (R)
	52	^((xx?)\2?|(((((((x{8})\9?)\8?)\7?)\6?)\5?)\4?)\3?)$	2013-12-20 15:18:10	Bisqwit (R)
	51	^(x|(xx){1,4}|((((((x{16})\8?)\7?)\6?)\5?)\4?)\3?)$	2013-12-20 15:26:55	Bisqwit (R)
	41	^(x|(xx){1,10}|(x{32}){1,4}|(x{32}){6,})$	2013-12-20 18:16:49	Iwonderifthisistaken (R)
	50	^(((((((((xx?)\9?)\8?)\7?)\6?)\5?)\4?)\3?)\2?)\1?$	2013-12-20 18:39:40	jensweh (R)
	30	^(((x|x{8}|x{128})\3?)\2?)\1?$	2013-12-20 18:43:08	pondscum (R)
	17	^(?!(.(..)+)\1*$)	2013-12-20 19:18:06	plby (GH)
		^(?!(x(xx)+)\1*$)
		^(?!((xx)+x)\1*$)
		^(?!((..)+.)\1*$)
	36	^(x{64})+$|^((((x?x)\5?)\4?)\3?)\2?$	2013-12-20 23:36:55	q1u2acker (R)
	33	^((x{8}){1,5}|(x{64})+|xx?|xxxx)$	2014-01-12 23:07:15	sneakyruds (R)
	31	^(((x|x{16}|x{256})\3?)\2?)\1?$	2014-02-12 16:09:28	Davidebyzero (GH)
	17	^((x+)(?=\2$))*x$	2014-02-21 21:30:06	Davidebyzero (GH,RG)
	17	^(?!(x*)(\1\1)+$)	2019-02-05	Grimy (GH)
Long count	14	almost certainly the 14-scoring one below	2014-01-07 12:27:38	timloh (RG~) (discovery date is earlier than indicated date)
	15	((.+)0\2[1]){8}	2014-01-15 06:28:48	abjr (GH)
	14	((.+)0\2+1){8}	2014-01-15 12:04:50	hugetoon (GH)
Alphabetical	78	^(?!.*(rne|eet |e.r...t|er.{6}r$))(a\S+\s)*(e\S+\s)*(r\S+\s)*([st]\S+(\s|$))*$	2013-12-25 05:25:31	muxrwc (GH)
	46	[^et] ren|[er]( \w+)\1|tate r|a t| ae|rt r|e e	2013-12-25 15:31:12	alexandrosm (GH)
	45	[^et] ren|[er]( \w+)\1|(tat|r). r|a t| ae|e e	2013-12-25 16:26:59	alexandrosm (GH)
	41	s ren|[er]( \w+)\1|(tat|r). r|a t| ae|e e	2013-12-25 16:59:02	alexandrosm (GH)
	37	r sn|( t\w+)\1|(tat|r). r|a t| ae|e e	2013-12-25 23:45:16	alexandrosm (GH)
	36	( .+[ts]..)\1|(tat|r). r|a t| ae|e e	2013-12-27 21:56:51	bbarry (GH)
	33	( .+[ts]..)\1|(tat|r). r|a t|e .r	2013-12-30 00:22:58	alexandrosm (GH)
	23	.r.{32}r|a.{10}te|n.n..	2013-12-31 17:04:35	alexandrosm (GH)
	23	almost certainly the above	2014-01-07 12:27:38	timloh (RG~) - probably copied alexandrosm's solution
	54	^(?!.* ((.*)t.* \2[es]|(.*)s.* \3[nr]|(.*)r.* \4[en]))	2014-01-13 00:25:24	dcwarwick (GH)
	43	^(?!.*( .*)(t.*\1[es]|s.*\1[nr]|r.*\1[en]))	2014-02-15 04:48:38	Davidebyzero (GH) - optimization of dcwarwick's solution
	22	[unpublished]	2018-02 ≈	LLB (RG)
Powers 2	19	^((x+)\2(?=\2$))*x$	2014-04-25 22:45:17	Davidebyzero (GH,RG)
	22	^(?!((xxx)+x|xx|)\1*$)	2014-09-18 03:05:37	muxrwc (GH)
	21	^(?!(x(xxx)+|xx)\1*$)		TH (RG), Davidebyzero (GH,RG)

Robust solutions

Level	Length	Regex	Domain	Date	Credit
Plain strings	3	foo	^[A-Za-z][a-z]*$
Anchors	4	ick$	^[A-Za-z][a-z]*ick[a-z]*$
Ranges	8	^[a-f]*$	^[a-z]+$
Backrefs	9	(...).*\1	^[a-z]+$
Abba	17	^(?!.*(.)(.)\2\1)	^[a-z]+$
A man, a plan	14	^(.)(.).*\2\1$
	40	^(.?)(.?)(.?)(.?)(.?)(.?).?\6\5\4\3\2\1$	^[a-z]+$*
Prime	14	^(?!(11+)\1+$)****	^11+$	1997-10-22 18:17:07	Abigail (P)
	-	^(11+?)\1+$*****	^11+$	1997-10-23 17:53:10	John L. Allen (P)
	14	^(?!(xx+)\1+$)	^xx+$
	15	^(?!(xx+|)\1+$)	^x*$***	2014-03-13 14:12:05	Davidebyzero (GH)
	-	^1?$|^(11+?)\1+$*****	^1*$	1997-11-19	Abigail (P)
	16	^(?!(xx+)\1+$)xx	^x*$	2014-03-13 14:50:18	teukon (GH)
	18	^(?=(xx+?)\1*$)\1$******	^x*$	2018-12-07	Davidebyzero (GH)
	18	(?=(x(x*))\1+$)\2^******	^x*$	2019-04-21	Grimy (GH)
Four	11	(.)(.\1){3}	^[A-Za-z][a-z]*$
Order	54	^a*b*c*d*e*f*g*h*i*j*k*l*m*n*o*p*q*r*s*t*u*v*w*x*y*z*$	^[a-z]+$
Triples	107	^([0369]|[258][0369]*[147]|([147]|[258][0369]*[258])([0369]|[147][0369]*[258])*([258]|[147][0369]*[147]))*$	^.+$	2013-03-27 21:49:49	joel
	107	^([0369]|[147][0369]*[258]|([258]|[147][0369]*[147])([0369]|[258][0369]*[147])*([147]|[258][0369]*[258]))*$	^.+$
	106	^(?=((.*?[147]){3})*((.*?[147]|){2}))(?=((.*?[258]){3})*((.*?[258]|){2})).*$(\3\7|\4\8(?!\3|\7)|(?!\4|\8))	^[0-9]+$	2014-02-13 to 2014-02-25	Davidebyzero & teukon (GH) (for full history, see below)
Glob	81	^(\*?)(\w*)(\*?)(\w*)(\*?)(\w*) .* ((?!\1).+|\1)\2((?!\3).+|\3)\4((?!\5).+|\5)\6$		2014-01-07 10:52:43	DiEvAl (GH) - created before hard mode; didn't match the domain of hard mode
	78	^(\*?)(.*)(\*?)(.*)(\*?)(.*) .* ((?!\1).+|\1)\2((?!\3).+|\3)\4((?!\5).+|\5)\6$		2014-01-15 20:35:11	teukon (GH) - DiEvAl's solution modified to assume that * never occurs to the right of matches
	84	^(.*)(\*?)(.*)(\*?)(.*)(\*?)(.*) .* \1((?!\2).+|\2)\3((?!\4).+|\4)\5((?!\6).+|\6)\7$	see below	2014-04-26 02:26:43	Davidebyzero (GH) - DiEvAl's solution modified to assume that * never occurs to the right of matches, and to match hard mode
Balance	37	^(<(<(<(<(<(<(<>)*>)*>)*>)*>)*>)*>)*$	^[<>]*$**
Powers	17	^(?!(x(xx)+)\1*$)	^x+$
	17	^((x+)(?=\2$))*x$	^x*$	2014-02-21 21:30:06	Davidebyzero (GH,RG)
	17	^(?!(x*)(\1\1)+$)	^x*$	2019-02-05	Grimy (GH)
Long count	31	^((?=(\S*)0).{4} (?=\2[1]))+1+$	^([01]{4}([1 ](?!$)|$)){16}$	2014-02-25	Davidebyzero (GH)
	35	^((?=(\S*)0).{4} (?=\2[1])){15}\2.$	^.*$	2014-02-25 22:33:53	teukon (GH)
Alphabetical	76	^(?!.*\b((.*)n.*\b\2[e]|(.*)r.*\b\3[ne]|(.*)s.*\b\4[rne]|(.*)t.*\b\5[srne]))	^([aenrst]{6} ?\b)+$	2014-01-09 06:49:57	AlanDeSmet (GH)
	58	^(?!.*\b(.*)(e|(n|r|(s|t))).* \1(a|(?!\3)[en]|(?!\4)[rs]))	^([aenrst]{6} ?\b)+$	2014-01-15 23:57:01	teukon (GH)
Powers 2	19	^((x+)\2(?=\2$))*x$	^x*$	2014-04-25 22:45:17	Davidebyzero (GH,RG)
	23	^(?!(x(xxx)+x?|xx)\1*$)	^x+$	2018-12-05	Davidebyzero (GH)
	24	^(?!(x(xxx)+x?|xx|)\1*$)	^x*$	2018-12-05	Davidebyzero (GH)

* A man, a plan - impossible in the general case, so this solution has a maximum robust length of 13 letters.
** Balance - impossible in the general case, so this solution has a maximum depth of 7 nesting levels.
*** If 1 is considered to be a prime number.
**** Included for historical purposes. Not technically a valid solution to this level since it works on 1s instead of xs.
***** Included for historical purposes. Not technically a valid solution to this level since it matches non-primes instead of primes and works on 1s instead of xs.
****** Of interest because of the implicit rather than explicit rejection of 0 and 1 as primes.

Robust solutions for Triples

Length	Regex	Domain	Date	Credit
229	^([0369]|[258][0369]*[147]|[147]([0369]|[147][0369]*[258])*[258]|[258][0369]*[258]([0369]|[147][0369]*[258])*[258]|[147]([0369]|[147][0369]*[258])*[147][0369]*[147]|[258][0369]*[258]([0369]|[147][0369]*[258])*[147][0369]*[147])*$	^.+$	2013-03-27 20:58:04	Alok Menghrajani
107	^([0369]|[258][0369]*[147]|([147]|[258][0369]*[258])([0369]|[147][0369]*[258])*([258]|[147][0369]*[147]))*$	^.+$	2013-03-27 21:49:49	joel
	^([0369]|[147][0369]*[258]|([258]|[147][0369]*[147])([0369]|[258][0369]*[147])*([147]|[258][0369]*[258]))*$	^.+$
255	^((?=(([^147]*[147]){3})*[^147]*$)(?=(([^258]*[258]){3})*[^258]*$)|(?=(([^147]*[147]){3})*[^147]*[147][^147]*$)(?=(([^258]*[258]){3})*[^258]*[258][^258]*$)|(?=(([^147]*[147]){3})*([^147]*[147]){2}[^147]*$)(?=(([^258]*[258]){3})*([^258]*[258]){2}[^258]*$))	^[0-9]+$	2014-02-13 07:11:40	Davidebyzero (GH)
241	^((?=(([^258]*[258]){3})*[^258]*$)(([^147]*[147]){3})*[^147]*|(?=(([^258]*[258]){3})*[^258]*[258][^258]*$)(([^147]*[147]){3})*[^147]*[147][^147]*|(?=(([^258]*[258]){3})*([^258]*[258]){2}[^258]*$)(([^147]*[147]){3})*([^147]*[147]){2}[^147]*)$	^[0-9]+$	2014-02-13 07:36:23	Davidebyzero (GH)
227	^((?=(([^258]*[258]){3})*[^258]*$)(([^147]*[147]){3})*|(?=(([^258]*[258]){3})*[^258]*[258][^258]*$)(([^147]*[147]){3})*[^147]*[147]|(?=(([^258]*[258]){3})*([^258]*[258]){2}[^258]*$)(([^147]*[147]){3})*([^147]*[147]){2})[^147]*$	^[0-9]+$	2014-02-13 09:52:00	Davidebyzero (GH)
222	^((?=(((([^258]*[258]){3})*[^258]*)|((([^258]*[258]){3})*[^258]*[258][^258]*)|((([^258]*[258]){3})*([^258]*[258]){2}[^258]*)|([^258]*))$)(([^147]*[147]){3})*(\6\6\9\9|\3\3\13\13[^147]*[147](\9\9|\6\6[^147]*[147]))[^147]*)$	^[0-9]+$	2014-02-13 14:43:43	Davidebyzero (GH)
180	^((?=((([^258]*[258]){3})*[^258]*))(?=((\2)|(\2[258][^258]*)|(\2([258][^258]*){2})|([^258]*))$)(([^147]*[147]){3})*(\7\7\8\8|\6\6\10\10[^147]*[147](\8\8|\7\7[^147]*[147]))[^147]*)$	^[0-9]+$	2014-02-13 14:51:01	Davidebyzero (GH)
	^((?=((([^258]*[258]){3})*[^258]*)(.*)$)(?=((\2)|(\2[258][^258]*)|(\2([258][^258]*){2})|(\3))$)(([^147]*[147]){3})*(\8\8\9\9|\7\7\11\11[^147]*[147](\9\9|\8\8[^147]*[147]))[^147]*)$	^[0-9]+$	2014-02-13 15:08:35	Davidebyzero (GH)
176	^((?=((([^258]*[258]){3})*[^258]*))(?=((\2)|(\2[258][^258]*)|\2([258][^258]*){2}|([^258]*))$)(([^147]*[147]){3})*(\7\7\8\8|\6\6\9\9[^147]*[147](\8\8|\7\7[^147]*[147]))[^147]*)$	^[0-9]+$	2014-02-13 15:29:20	Davidebyzero (GH)
170	^((?=((([^258]*[258]){3})*[^258]*))(?=((\2)|(\2[258][^258]*)|\2([258][^258]*){2}|([^258]*))$)(([^147]*[147]){3})*(\7\7\8\8|\6\9[^147]*[147](\8\8|\7[^147]*[147]))[^147]*)$	^[0-9]+$	2014-02-13 15:36:30	Davidebyzero (GH)
169	^((?=((([^258]*[258]){3})*[^258]*))(?=((\2)|((\2[258][^258]*)|\2([258][^258]*){2})|([^258]*))$)(([^147]*[147]){3})*(\7\7|\6\10[^147]*[147](\9\9|\8[^147]*[147]))[^147]*)$	^[0-9]+$	2014-02-13 15:47:33	Davidebyzero (GH)
168	^((?=((([^258]*[258]){3})*[^258]*))(?=(((\2[258][^258]*)|\2([258][^258]*){2})|((\2)|([^258]*)))$)(([^147]*[147]){3})*(\6\6|\9[^147]*[147](\8\8|\7[^147]*[147]))[^147]*)$	^[0-9]+$	2014-02-13 15:52:22	Davidebyzero (GH)
164	^((?=((([^258]*[258]){3})*[^258]*))(?=(((\2[258][^258]*)|\2([258][^258]*){2})|(\2|[^258]*))$)(([^147]*[147]){3})*(\6\6|\9[^147]*[147](\8\8|\7[^147]*[147]))[^147]*)$	^[0-9]+$	2014-02-13 15:53:11	Davidebyzero (GH)
163	^((?=((([^258]*[258]){3})*[^258]*))(?=(((\2[258][^258]*)|\2([258][^258]*){2})|(\2[^258]*))$)(([^147]*[147]){3})*(\6\6|\9[^147]*[147](\8\8|\7[^147]*[147]))[^147]*)$	^[0-9]+$	2014-02-13 15:59:11	Davidebyzero (GH)
156	^((?=((([^258]*[258]){3})*[^258]*))(?=(((\2[258][^258]*)|\2([258][^258]*){2})|(\2))$)(([^147]*[147]){3})*(\6\6|\9[^147]*[147](\8\8|\7[^147]*[147]))[^147]*)$	^[0-9]+$	2014-02-13 16:02:02	Davidebyzero (GH)
156	^((?=((([^258]*[258]){3})*[^258]*))(?=((\2([258][^258]*)|\2([258][^258]*){2})|(\2))$)(([^147]*[147]){3})*(\6\6|\9[^147]*[147](\8\8|\7[^147]*[147]))[^147]*)$	^[0-9]+$	2014-02-13 16:09:21	Davidebyzero (GH)
158	^((?=((([^258]*[258]){3})*[^258]*))(?=((\2)|((\2[258][^258]*)|(\2([258][^258]*){2})))$)(([^147]*[147]){3})*(\7\7|\6[^147]*[147](\9\9|\8[^147]*[147]))[^147]*)$	^[0-9]+$	2014-02-13 16:15:43	Davidebyzero (GH)
156	^(?=((([^258]*[258]){3})*[^258]*))(?=((\1)|((\1[258][^258]*)|(\1([258][^258]*){2})))$)(([^147]*[147]){3})*(\6\6|\5[^147]*[147](\8\8|\7[^147]*[147]))[^147]*$	^[0-9]+$	2014-02-14 13:29:23	Davidebyzero (GH)
153	^(?=(([^258]*[258]){3})*[^258]*([258][^258]*([258][^258]*)?)?$)(([^147]*[147]){3})*(?=([^147]*))\7((?!\3)(?=([147][^147]*))\9((?!\4)[147][^147]*|\4)|\3)$	^[0-9]+$	2014-02-15 06:45:47	Davidebyzero (GH)
157	^(?=[^147]*([147]?)[^147]*([147]?)[^147]*(([147][^147]*){3})*$)[^258]*((?=.*$\1)|(?!.*$\1)[258])[^258]*((?=.*$\2)|(?!.*$\2)[258])[^258]*(([258][^258]*){3})*$	^[0-9]+$	2014-02-16 20:55:58	teukon (GH) (discovery date is probably earlier)
153	^(?=(([^258]*[258]){3})*[^258]*([258]?)[^258]*([258]?)[^258]*$)(([^147]*[147]){3})*(?=([^147]*))\7((?!\3)(?=([147][^147]*))\9((?!\4)[147][^147]*|\4)|\3)$	^[0-9]+$	2014-02-17 11:36:59	Davidebyzero (GH)
145	^(?=(([^258]*[258]){3})*[^258]*([258]?)[^258]*([258]?)[^258]*$)(([^147]*[147]){3})*(?=([^147]*))\7((?!\3)(?=(.[^147]*))\9((?!\4).[^147]*|\4)|\3)$	^[0-9]+$	2014-02-17 20:23:11	teukon (GH)
	^(?=[^147]*([147]?)[^147]*([147]?)[^147]*(([147][^147]*){3})*$)(?=([^258]*))\5(\1|(?!\1).)(?=([^258]*))\7(\2|(?!\2).)[^258]*(([258][^258]*){3})*$	^[0-9]+$	2014-02-17 20:23:11	teukon (GH)
137	^(?=(([^258]*[258]){3})*[^258]*(.?)[^258]*(.?)[^258]*$)(([^147]*[147]){3})*(?=([^147]*))\7((?!\3).|\3)(?=([^147]*))\9((?!\4).|\4)[^147]*$	^[0-9]+$	2014-02-18 08:01:51	Davidebyzero (GH)
	^(?=[^147]*(.?)[^147]*(.?)[^147]*(([147][^147]*){3})*$)(?=([^258]*))\5(\1|(?!\1).)(?=([^258]*))\7(\2|(?!\2).)[^258]*(([258][^258]*){3})*$	^[0-9]+$	2014-02-18 08:01:51	Davidebyzero (GH)
	^(?=[^147]*(.?)[^147]*(.?)[^147]*(([147][^147]*){3})*$)(?=([^258]*))\5(?=(\1|.))\6(?=([^258]*))\7(?=(\2|.))\8[^258]*(([258][^258]*){3})*$	^[0-9]+$	2014-02-18 08:01:51	Davidebyzero (GH)
127	^(?=(([^147]*[147]){3})*[^147]*(.?)[^147]*(.?))(?=(([^258]*[258]){3})*[^258]*(.?)[^258]*(.?))\d+$(\3\7|\4\8(?!\3|\7)|(?!\4|\8))	^.*$	2014-02-18 12:23:02	Davidebyzero (GH)
126	^(?=(([^147]*[147]){3})*[^147]*(.?)[^147]*(.?))(?=(([^258]*[258]){3})*[^258]*(.?)[^258]*(.?)).+$(\3\7|\4\8(?!\3|\7)|(?!\4|\8))	^[0-9]*$	2014-02-18 12:23:02	Davidebyzero (GH)
119	^(?=((.*?[147]){3})*[^147]*(.?)[^147]*(.?))(?=((.*?[258]){3})*[^258]*(.?)[^258]*(.?))\d+$(\3\7|(?!\3|\7)\4\8|(?!\4|\8))	^.*$	2014-02-18 18:55:50	teukon (GH)
118	^(?=((.*?[147]){3})*[^147]*(.?)[^147]*(.?))(?=((.*?[258]){3})*[^258]*(.?)[^258]*(.?)).*$(\3\7|(?!\3|\7)\4\8|(?!\4|\8))	^[0-9]*$	2014-02-18 18:55:50	teukon (GH)
111	^(?=((.*?[147]){3})*(((.*?[147])?){2}))(?=((.*?[258]){3})*(((.*?[258])?){2}))\d+$(\3\8|\4\9(?!\3|\8)|(?!\4|\9))	^.*$
110	^(?=((.*?[147]){3})*(((.*?[147])?){2}))(?=((.*?[258]){3})*(((.*?[258])?){2})).*$(\3\8|\4\9(?!\3|\8)|(?!\4|\9))	^[0-9]+$	2014-02-19 10:48:11	Davidebyzero (GH)
107	^(?=((.*?[147]){3})*((.*?[147]|){2}))(?=((.*?[258]){3})*((.*?[258]|){2}))\d+$(\3\7|\4\8(?!\3|\7)|(?!\4|\8))	^.*$
106	(?=((.*?[147]){3})*((.*?[147]|){2}))(?=((.*?[258]){3})*((.*?[258]|){2}))^.*$(\3\7|(?!\3|\7)\4\8|(?!\4|\8))	^[0-9]+$	2014-02-25 01:50:02	teukon (GH)
106	^(?=((.*?[147]){3})*((.*?[147]|){2}))(?=((.*?[258]){3})*((.*?[258]|){2})).*$(\3\7|\4\8(?!\3|\7)|(?!\4|\8))	^[0-9]+$

Robust solutions for Powers of various bases

Base	Length	Regex	Domain	Date	Credit
0	2	^$	^x*$
1	3	^x$	^x*$
2	17	^((x+)(?=\2$))*x$	^x*$	2014-02-21 21:30:06	Davidebyzero (GH,RG)
	17	^(?!(.(..)+)\1*$)	^x+$	2013-12-20 19:18:06	plby (GH)
	17	^(?!(x(xx)+)\1*$)	^x+$
	18	^(?!(x(xx)+|)\1*$)	^x*$	2014-03-13 13:21:03	Davidebyzero (GH)
	17	^(?!(x*)(\1\1)+$)	^x*$	2019-02-05	Grimy (GH)
3	19	^((x+)\2(?=\2$))*x$	^x*$	2014-04-25 22:45:17	Davidebyzero (GH,RG)
	23	^(?!(x(xxx)+x?|xx)\1*$)	^x+$	2018-12-05	Davidebyzero (GH)
	24	^(?!(x(xxx)+x?|xx|)\1*$)	^x*$	2018-12-05	Davidebyzero (GH)
	25	^(?!((xxx)*(xx)\3?|)\1*$)	^x*$	2018-12-05	Davidebyzero (GH)
	31	^(?!(x*)(?!(\1\1)(\1\2)*$)\1+$)	^x+$	2019-02-08	Davidebyzero (GH)
	30	^(?!(x*)(?!\1\1(\1{3})*$)\1+$)	^x+$	2019-02-08	Davidebyzero (GH)
	26	^(?!(x*)(\1|(\1{3})+\1?)$)	^x*$	2019-02-08	Davidebyzero (GH)
4	21	^((x+)\2\2(?=\2$))*x$	^x*$	2018-12-05	Davidebyzero (GH)
5	22	^((x+)\2{3}(?=\2$))*x$	^x*$	2018-12-05	Davidebyzero (GH)
	33	^(?!(x(x{5})+x?x?x?|xxx?x?|)\1*$)	^x*$	2018-12-05	Davidebyzero (GH)
	33	^(?!(x(x{5})+x{0,3}|x{2,4}|)\1*$)	^x*$	2018-12-05	Davidebyzero (GH)
	31	^(?!(xx(x{5})*(x{4}|x?x?))\1*$)	^x+$	2018-12-05	Davidebyzero (GH)
	32	^(?!(xx(x{5})*(x{4}|x?x?)|)\1*$)	^x*$	2018-12-05	Davidebyzero (GH)
	32	^(?!(x*)(?!(\1{4})(\1\2)*$)\1+$)	^x+$	2019-02-08	Davidebyzero (GH)
	31	^(?!(x*)(?!\1{4}(\1{5})*$)\1+$)	^x+$	2019-02-08	Davidebyzero (GH)
	34	^(?!(x*)(\1?\1?(\1|(\1{5})+\1?))$)	^x*$	2019-02-08	Davidebyzero (GH)
	35	^(?!(x*)(\1{1,3}|(\1{5})+\1{0,3})$)	^x*$	2019-02-08	Davidebyzero (GH)
6	22	^((x+)\2{4}(?=\2$))*x$	^x*$	2014-02-21 21:40:31	teukon (GH)
7	22	^((x+)\2{5}(?=\2$))*x$	^x*$	2018-12-05	Davidebyzero (GH)
	32	^(?!(x(x{7})+x{0,5}|x{2,6})\1*$)	^x+$	2018-12-05	Davidebyzero (GH)
	33	^(?!(x(x{7})+x{0,5}|x{2,6}|)\1*$)	^x*$	2018-12-05	Davidebyzero (GH)
	34	^(?!(xx(x{7})*(x{6}|x{0,4})|)\1*$)	^x*$	2018-12-05	Davidebyzero (GH)
	32	^(?!(x*)(?!(\1{6})(\1\2)*$)\1+$)	^x+$	2019-02-08	Davidebyzero (GH)
	31	^(?!(x*)(?!\1{6}(\1{7})*$)\1+$)	^x+$	2019-02-08	Davidebyzero (GH)
	35	^(?!(x*)(\1{0,4}(\1|(\1{7})+\1?))$)	^x*$	2019-02-08	Davidebyzero (GH)
	35	^(?!(x*)(\1{1,5}|(\1{7})+\1{0,5})$)	^x*$	2019-02-08	Davidebyzero (GH)
8	22	^((x+)\2{6}(?=\2$))*x$	^x*$	2018-12-05	Davidebyzero (GH)
9	22	^((x+)\2{7}(?=\2$))*x$	^x*$	2018-12-05	Davidebyzero (GH)
10	22	^((x+)\2{8}(?=\2$))*x$	^x*$	2018-12-05	Davidebyzero (GH)
11	22	^((x+)\2{9}(?=\2$))*x$	^x*$	2018-12-05	Davidebyzero (GH)
	34	^(?!(x(x{11})+x{0,9}|x{2,10})\1*$)	^x+$	2018-12-05	Davidebyzero (GH)
	35	^(?!(x(x{11})+x{0,9}|x{2,10}|)\1*$)	^x*$	2018-12-05	Davidebyzero (GH)
	33	^(?!(x*)(?!(\1{10})(\1\2)*$)\1+$)	^x+$	2019-02-08	Davidebyzero (GH)
	33	^(?!(x*)(?!\1{10}(\1{11})*$)\1+$)	^x+$	2019-02-08	Davidebyzero (GH)
	36	^(?!(x*)(\1{0,8}(\1|(\1{11})+\1?))$)	^x*$	2019-02-08	Davidebyzero (GH)
	36	^(?!(x*)(\1{1,9}|(\1{11})+\1{0,9})$)	^x*$	2019-02-08	Davidebyzero (GH)
12	23	^((x+)\2{10}(?=\2$))*x$	^x*$	2018-12-05	Davidebyzero (GH)
13	23	^((x+)\2{11}(?=\2$))*x$	^x*$	2018-12-05	Davidebyzero (GH)
	35	^(?!(x(x{13})+x{0,11}|x{2,12})\1*$)	^x+$	2018-12-05	Davidebyzero (GH)
	36	^(?!(x(x{13})+x{0,11}|x{2,12}|)\1*$)	^x*$	2018-12-05	Davidebyzero (GH)
	33	^(?!(x*)(?!(\1{12})(\1\2)*$)\1+$)	^x+$	2019-02-08	Davidebyzero (GH)
	33	^(?!(x*)(?!\1{12}(\1{13})*$)\1+$)	^x+$	2019-02-08	Davidebyzero (GH)
	37	^(?!(x*)(\1{0,10}(\1|(\1{13})+\1?))$)	^x*$	2019-02-08	Davidebyzero (GH)
	38	^(?!(x*)(\1{1,11}|(\1{13})+\1{0,11})$)	^x*$	2019-02-08	Davidebyzero (GH)

If the domain of Glob must be stated in a single regex, it would be:
^([a-z]*)\*?([a-z]*)\*?([a-z]*)\*?([a-z]*) matches \1[a-z]*\2[a-z]*\3[a-z]*\4$
However, it may actually have 4 domains:
^([a-z]*)\*([a-z]+)\*([a-z]*) matches \1[a-z]*\2[a-z]*\3$
^\*([a-z]+)\*([a-z]+)\* matches [a-z]+\1[a-z]+\2[a-z]+$ (left only)
^([a-z]+)\*([a-z]+) matches [a-z]*\1[a-z]+\2[a-z]*$ (right only)
^\*?([a-z]+)\*? matches [a-z]*\1[a-z]*$

The domains above may be controversial, as we have a limited sampling. Feel free to discuss them in this Gist.

Triples (107) DFA solution, pretty-printed:

^( [0369] | [258][0369]*[147] |
  ( [147] | [258][0369]*[258])
  ([0369] | [147][0369]*[258])*
  ( [258] | [147][0369]*[147]))*$

Triples (106) lookahead + backreferences solution, pretty-printed:

^(?=((.*?[147]){3})*((.*?[147]|){2}))
 (?=((.*?[258]){3})*((.*?[258]|){2}))
 .*$(\3\7 | \4\8(?!\3|\7) | (?!\4|\8))

Glob (84), pretty-printed:

^(.*)(\*?)
 (.*)(\*?)
 (.*)(\*?)(.*) .* \1((?!\2).+|\2)
                  \3((?!\4).+|\4)
                  \5((?!\6).+|\6)\7$

Oh, the Alphabetical domain string is slightly off. It should be something like ^([aenrst]{6} ){6}[aenrst]{6}$ or ^([aenrst]{6}( (?!$)|$)){7}$.

Surely, for Glob, the domain is something like:

^(?! )([a-z]*\*)*[a-z]* matches [a-z]+$

or one I like less but you may well prefer:

^([a-z]+|\*)+ matches [a-z]+$

A solution would then not be robust but "robust with respect to domain X".

I like this idea. :)

Oh, the Alphabetical domain string is slightly off. It should be something like ^([aenrst]{6}( (?!$)|$)){7}$.

I put the domain as ^([aenrst]{6}( (?=.)|$)){7}$ at first, but after some thought I simplified it because it seemed to me that the lookahead wasn't needed. But now I realize that I was right the first time, not the second.

I like your (?!$) better than my (?=.), so I will use it.

^(?! )([a-z]*\*)*[a-z]* matches [a-z]+$
^([a-z]+|\*)+ matches [a-z]+$

What is the purpose of the (?! )?

I don't think either of these domains would be possible to solve robustly in an ECMAScript style regex.

Although at some point we might want to start expanding our game to include more powerful regex variants (i.e. PCRE). But not yet. There's still more we can do inside the limits imposed by ECMAScript.

What is the purpose of the (?! )?

Just to keep the left-part non-empty. I've noticed we often dodge the empty string. These are just suggested domains. If you think that matches is in the domain or that b**n matches begin is not in the domain, you'd need something different.

As before, I'm not intending to resolve ambiguities, but simply appreciate that different people can have different, consistent ideas about the pattern/domain. This is why I was so careful with my own problems, selecting right-side strings to kill off natural alternative patterns (Matryoshka) and to clarify the domain as much as possible (Latin squares). I also prioritised domain simplicity over other factors (in Tic-tac-toe, I opted for the domain of random boards of O, X, and ., rather than the more complex domain of valid game positions). Even after all this I decided it would be best to give domain regexes at the outset and hope that the pattern in each problem is reasonably unambiguous.

I don't think either of these domains would be possible to solve robustly in an ECMAScript style regex.

Nor do I, which is why I say this problem is impossible, along with Balance and "A man, a plan". I think the best one can do is a schema of regexes, based on some simple parameter (where the function taking a value of the parameter and returning a corresponding regex should be as simple as possible).

For "Balance" and "A man, a plan", you've already done this by selecting parameters, respectively nesting depth and string length, and giving an example for each.

This can be done for "Glob" too. The number of asterisks would be my parameter of choice, but I think I'm in the minority here.

Of course, things get really subjective here. Personally, I'd be tempted to flag each of these problems as having "no known robust solution", allowing each to score 0 for the purposes of the robust total. I'd then go on to briefly discuss each problem below. However, I certainly understand you wanting to put seemingly natural bounded-robust solutions in for the sake of completeness.

Solution for it never ends:
u\b

Do you have any plans for similar documents for the Teuken and Holiday puzzle sets? For the Holiday set, I'd be happy to contribute my non-optimal solutions (and I'd love to get a non-optimal solution for Quine, which I've been stuck on for years >_< ).

Have you seen my old Regex Golf page? I don't think it has any solutions you haven't covered here, but it does have additional commentary on each problem, including the old problem descriptions, so might be of interest for other readers of this gist.

One last thing, I sent you an email yesterday(ish) about the Regex of Regex problem. Since I didn't think to mention it at the time, I'll confirm now that I am the Dinoguy1000 from the leaderboard with the 30-score solution to that problem.

I am actually working on a Teukon compilation just like I did for Classic, and will follow that up with Holiday as well. But the solutions that aren't public, I will publish as hashes (md5sum or otherwise)... unless you give me a convincing argument to publish everything in the clear :-) The thing holding me back from doing so is the leaderboard. Back when I discussed the Classic level set on a github gist (when it was the only level set, thus not called Classic) there was no public leaderboard. Now there is, and it's filled with people who just copied the best published solution. If the leaderboard had timestamps, that'd be much less of a problem, and I'd be much more willing to publish.

Good luck with Quine! It's actually not nearly as hard as it seems at first... look closely at the test cases. There's a very predictable pattern to them. But I feel ya. I got so frustrated with it, that to get my first working solution, I cheated and modified an existing regex quine I found on the web to work for this problem. And then when I realized that the pattern in the test cases could be exploited, I kicked myself for not trying harder to do it entirely on my own. I did have a lot of fun with it, and found a wide variety of solutions and cataloged them (of which there are two distinct families, not even counting strict quines like the one I used at first... and perhaps a third which would be much harder to do, if possible). Beware, whatever method you use to solve it Quine, once you do, don't give in to the temptation of clicking the [spoiler] tag. It's much more fun to come upon that particular technique on your own.

And yep, I enjoyed reading your 2015 gist post and wiki article back in 2018 :-)

Right, I came across an older comment of yours in which you said much the same about publishing solutions, shortly after I saved my comment here. I agree publishing hashes is the way to go for now (or at least, I have no convincing arguments for publishing plaintext solutions), though at the same time I wonder how useful they would be - even for just one of the 30-score solutions for Regex of Regex that I've come up with, I could trivially generate thousands of variants, each of which would have a unique hash, just by swapping around subclauses in the regex or rearranging the characters in character classes. So it would probably be a good idea to come up with a standard way to represent each solution before generating and publishing any hashes of them.

I'll definitely keep that in mind, though I'm nowhere near as skilled with regexes as you are (in all honesty, I probably wouldn't have come up with my 30-score Regex of Regex solutions, or my 66-score Countries solutions, without the help of a regex golf solution generator I found online, and even then it took some time of staring at the puzzles and generated solutions to golf them down any further). I would at least like to know if the Quine puzzle is the last one in the Teuken set, or if there are any more after it; I've been curious about this for a very long time now. =) It certainly feels like a final puzzle, and I shudder to imagine what monstrosities might follow it if it isn't. =D

I've had an idea for some time about a possible method to check for optimally-golfed solutions for at least some of the puzzles, but lack the ability to act on it. If you're interested, I'd love to discuss it some in email.

@Hammad1007 See the explanations in the "Solutions" dropdowns on my Regex Golf page. If you still have questions after that, I can try to answer them for you, as long as you're more specific. =)