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#745, September 29 - October 5:
The Weekly Extreme Str8ts Puzzle

by Andrew Stuart
WARNING: This is the Weekly 'Extreme' Str8ts.
Only attempt this puzzle if you have time and patience.
Using the solver will not help you. (much).
Archive
Since there has been interesting strategy discussion on these puzzles and by popular request, I have opened an archive on the last thirty weeks. The discussion section is open for continued posting.
Share and Enjoy
Puzzles 1 to 250 are available as Puzzle Packs, just $5.49.

Discussion...
Posts you have NOT read are in normal colors, older ones are in grey.
Please email me if you experience problems or bugs. Cheers, Andrew Stuart


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by: Ursula

1-Oct-2024, 19:32
Solved it with several hints after running desperate into contradictions the last two days.
Interesting solving with "community's help, however I prefer to puzzle alone (or with one hint at most)
Thx to OneGuess I'll have peace fir the rest of the week.
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by: OneGuess

 30-Sep-2024, 10:47
ABC5 low (jgrab or chain), AB 9 high (chain), several URs e.g. no 1 in EF6, no 4/5 in D89, no 2/3 in H2, no 9 in AB6, all columns and rows contain 7 and 8, and 2 more chains - 5 hours to solve and I wonder what I would do on Sundays without Andrew‘s 5 stars
 

by: optimator

 30-Sep-2024, 16:11
oof: after your comment I think I'll pass, as I have plenty of other things to do.
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by: jgrab

 29-Sep-2024, 10:12
ABC5=hi soon runs into problems. But the rest remains difficult enough to become desperate ...
 

by: Marya

 1-Oct-2024, 11:30
 I tried ABC5=hi, but I did not find any problems. Seems everyone has given up solving this without hints?
 

by: RudiK

 1-Oct-2024, 11:40
 I was able to solve it with hago's hints (C7 & H4).
But what really interests me is: how does he get to the solution of these two fields? That answer would be of great value to me.
 

by: kozibrada

 1-Oct-2024, 16:06
 @RudiK: These “key” cells are visible after solving. There are surely more like that; maybe is even enough one additional clue to relative easy solving (didn’t prove).
 

by: aw

 1-Oct-2024, 16:26
 @Marya: I solved it ignoring the hints, probably very similar to OneGuess above: By _falsifying_ (with sometimes nearly endless chains)

- ABC5 high (else B9=D9=2)
- AB9 low
- 3 not in C
- 4 in C245 (three separate chains!)
- F6=5
- C8=7
- B7=4

and then wings on 7,8,9 and various URs. Elegance is something different ... Fortunately it was all trial and error - I dislike trial and success <:-)
 

by: kozibrada

 1-Oct-2024, 17:32
 My way:
1) As jgrab, I began ABC = hi. Used the rule of parity: if ABC5 = hi → 34 (of maximum of 36 possible in the 9×9 grid) sure even numbers in cols… two in rows are missing, so row G must contain all even numbers → G123 = [234] → G5 = 6 or 8 ↔ contradiction. ABC5 = lo.

… X-wing on 7 … (didn’t try AB9 = lo, but this doesn’t help much) …

2) Used a quite long chain with several UR’s, but one of them (advance) is beautiful. Again ABC5: if ABC5 = [234] → (the rule of parity) G = 6 or 8, G123 = [234]; E3 and G3 = [34] → H3 = 56; also H5 = 56 → G12 and H12 = [234]… to avoid non-uniqueness, GH2 must contain 4; D3 = 8, D2 = 9 → C2 = 7, C1 = 8 (and B1 = 5)… Setti on 8 is full. J6 must be different from 8 (the rule of parity), therefore AB6 = [789]… but now we have 2×3 UR [789] in AB689 (AB2 isn’t equal to 7, 9 nor 8). ABC5 = [123].

… ABC4 = hi (UR) …

3) Short chain / SI / “sudoku logic”: C4 = 3 with C7 = 6 give UR [45] in AB47… C12 = lo creates this inconvenience, thus C12 = hi.

… then some eliminations and again that UR problem, the rest is about an X-wing, Settis.
 

by: Marya

 1-Oct-2024, 18:34
@aw, kozibrada:
I used hago‘s hints, and they quite quickly lead me to ABC5=low…
I‘ll have to check your solutions as soon as I find the time.
Thanks for your answers!
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by: kst extra 3/11

 29-Sep-2024, 06:07
 

by: tg

 29-Sep-2024, 08:37
 Relatively easy. Needed a short chain towards the end. - Thanks!
 

by: kmr

 29-Sep-2024, 08:53
 Like tg. Runs smoothly except the decision on h/l in column 5.
 

by: optimator

 29-Sep-2024, 14:59
 like kmr
 

by: Loser

 29-Sep-2024, 17:11
 THX by for the nice kst-set
 

by: Martinus

 30-Sep-2024, 10:22
 Very nice set. Needs good looks first on diagonals, and then some small easy chains in the bottom right corner. Thanks, kst!
 

by: kris

 30-Sep-2024, 12:26
 SI at the critical point: 2 on C5 produces an instant conflict in col 2.
The rest is solvable by standard BX tools.
 

by: BP

 30-Sep-2024, 20:00
 Chainfree fun. Used a very skewed xwing to finish.
 

by: Auwei

 4-Oct-2024, 08:54
@bp: maybe the following step(s):
H8=9? J9=6,F6=8,J6=?
perfect puzzle for a rainy friday
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by: kst extra 3/11

 29-Sep-2024, 06:07
 

by: BP

 29-Sep-2024, 08:27
 This puzzle is simply beautiful. Looks pretty hard at first, but solvable with standard B tools. Many thanks, kst, if you're reading this!
 

by: Martinus

 29-Sep-2024, 21:21
 Like BP. Very, very nice.
 

by: optimator

 30-Sep-2024, 15:47
 like BP
 

by: OneGuess

 2-Oct-2024, 10:55
 lots of fund but found it difficult - up to a point where I found out (with a chain) that all rows and all columns contain 5 - still had to guess once (low high on G4). happy to receive tips how to solve without my guess
 

by: BP

 2-Oct-2024, 11:58
 Here are my first steps:

B-Setti: 2,6 in Boxes 4,5,6 => 2,6 in D

B-Setti: 4,7 in D,E,F => 4,7 in Box 5.

Note: 4,7 not together in EFG4, therefore F5=47

B-Setti: 3,4,5,6,7 in cols 7,8,9 => 3,4,5,6,7 in Box 9 (hidden quintuple)

Note: Either G789=345, H89=67 or G789=567,H89=34

CE in H and Box 7: 1,2 not in H. Therefore 9 in H. Single: H5=9

CE in Box 8: G5<=5. This determines high/low in G: G789=567, G345=234

CE in col 4, Box 5: G4<=4 => 7,8 not in EF4 => EF4=45,G4=3, ...
 

by: BP

 2-Oct-2024, 11:59
 @OneGuess: Do you know my tutorial on B-Str8ts Strategies in the main menu?
 

by: OneGuess

 2-Oct-2024, 14:42
 @BP: thank you - saw your tutorial in B-Str8ts just now - very helpful! Me guessing (low/high on G4) on this puzzle has more to do with my limited brain power - now that I know the solution, I can do this (this time - not valid for next puzzle next week :—)
But always fun!
 

by: JL

 3-Oct-2024, 06:56
 Thanks BP for the steps. Makes puzzles more enjoyable and helps with future puzzles. Cheers
 

by: BP

 3-Oct-2024, 08:45
 @JL, OneGuess: If you like this kind of B puzzle (hard, but solvable with standard B tools) and are looking for an extra exercise: In week #718 hone posted another beauty: hone718_8004_Bow_B. And you may find all my crucial steps below.

 

by: kmr

 3-Oct-2024, 18:57
 Thanks for the steps. Great ideas for better using the B, BP.
 

by: JL

 4-Oct-2024, 02:38
Thanks BP. Appreciate the suggestion and the steps. Cheers
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by: kst extra 3/11

 29-Sep-2024, 06:06

 

by: BP

 29-Sep-2024, 08:27
 Great challenge! Besides standard tools we used two SIs and a very skewed x-wing.
 

by: jgrab

 29-Sep-2024, 10:58
 Thanks, nice! Needs the right hi/lo decision on the upper left diagonal.
 

by: Martinus

 29-Sep-2024, 15:32
 Like BP. Thanks!
 

by: optimator

 30-Sep-2024, 16:09
 15', like jgrab
 

by: Auwei

 1-Oct-2024, 08:41
It took me quite a while, but I enjoyed every minute. What a beautiful legacy, thank you kst!
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by: kst extra 3/11

 29-Sep-2024, 06:05

 

by: charliepat

29-Sep-2024, 16:00
 Done, with a small chain. Wrong decision in C3 leads to a contradiction quite quickly. Enjoyed it very much, thanks kst!
 

by: jgrab

 29-Sep-2024, 19:21
 A smooth one, thanks.
 

by: E.H.

 29-Sep-2024, 21:02
 I did it like charliepat. It´s a nice one, not as hard as the other one.
 

by: kris

 30-Sep-2024, 15:07
 Thanks a lot, kst and BP, for a great set!
 

by: kmr

 30-Sep-2024, 16:43
 Thanks for this nice puzzle.
 

by: optimator

 30-Sep-2024, 20:11
 not hard, no chains; thanks!
 

by: BP

 30-Sep-2024, 20:57
Smooth work with an UR. Many thanks for the set!
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  • 75 min-Dont like that kind of hints.Try by mys.the options.You can call it a headchain writing on paper.2 times failed.Than it was done:)
    - effchen
  • 47:05 - but only with hints from proteus and the soloist ...
    - Latimer
  • The last hint from proteus made it collapse. Thx
    - Fred
  • Verdampt schwer, Stunden und Tage
    - zoo-pony
  • 10 min with all hints
    - relijo
  • Schwer! 2 Tage mit Raten versucht und gescheitert. Mit der Hilfe von C7=5 und H4=2 (Danke!), aus der auch G9=6 folgt, geschafft.
    - b*k*
  • with all hints
    - chris
  • B5=1 makes it solvable with standard tools
    - proteus
  • yes, G9 is 6
    - dersoloist
  • Is G9 really 6? Several failurrs..
    - Cleo
  • Viele Versuche, mit 2 Hints in 3 Tagen gelöst. Extrem.
    - S. Walt
  • 2 days, 7 hours, 37 minutes
    - puzzled
  • Took many tries and elimination. Hard one.
    - Essie
  • had to use all the hints, still took me 50 min. No fun.
    - juehe
  • Got lost several times
    - Ursula
  • hago's hints: C7 = 5 H4 = 2
    - Ske
  • you can solve it without chains, if you assume - additional to hago's hints - that G9 = 6
    - Ske
  • 1 hour 4 min with hints
    - Maven
  • 37 Minuten - danke an hago
    - BertRam
  • 15 min with hints
    - EC
  • viel zu schwer, das war ein 6sterner, nur mit aller hilfe nach 2 tagen gelöst.
    - dersoloist
  • Used both hints, but n o success. Chains or "(lucky) guesses" i don't make.
    - Fred
  • 90' with hints and guess
    - Richard
  • At last I did it with a little help of my (unknown) friend hago and a lucky hand.
    - E.H.
  • thx to hago solved, still one chain needed
    - easydoesit
  • and lucky guess in B3/B5.
    - barbara
  • 39', only with both hints, otherwise (some attempts) no chance. Thanks!
    - barbara
  • 34 min mit den beiden Hinweisen von hago (Danke!) und gut geraten
    - Rot
  • 24'24 - took both hints (thanks to hago) and still needed two ugly guesses in D9 and D3.
    - Beate
  • 26min, only with the two hints and a few guesses solvable for me. A really hard nut
    - Martin
  • 58', quite a hard nut...
    - l.
  • after 3 times where I failed, I could solve it only with a chain....
    - Emma
  • H4 = 2
    - hago
  • one hint is to less for me. can i get another one ? thanx
    - dersoloist
  • is this solvable without "hint". Got stuck again even after hint revealed quite a bit. Intuitive chain from d9 led to a smooth finish.
    - cs
  • 50 min - no clear path for me
    - Loser
  • even with the hint, too many chains neede, so I got lost
    - easydoesiit
  • 40' - tricky, needed that hint and some chaining - found no real start
    - COM
  • 20 min with the hint - after trying the whole morning. Thx a lot, hago :)
    - Susi
  • Took me more than 90 min; many chains, and no good idea.
    - jgrab
  • 23 min. - needed several chains. A real 5 star. Thank you, Andrew
    - Nessi
  • C7 = 5 may help
    - hago
  • I give up...
    - Susi
  • still waiting for idea how to begin
    - Gerd
  • yes, still sleeping. Just opened the page started actually. Let's see...
    - ttbass
  • everybody still sleeping?
    - straddict