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#784, June 29 - July 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).
Oct 18th 2024
The solver can now handle Str8ts variants. Yay! The solver button on the player will now pass an appropriate parameter.
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.
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Discussion...
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Please email me if you experience problems or bugs. Cheers, Andrew Stuart


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by: aw

 30-Jun-2025, 09:05
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Maybe it is not exactly the right place for this question, but because the spectrum around B and Jigsaw is already tangled here:

A standard Sudoku is a priori a B-Problem; and the "Killer"-variety of Sudokus already exist as (standard) B-Sudokus and Jigsaw-Sudokus - is there a reason why there are no "standard" Jigsaw-Sudokus (with Jigsaw-blocks instead of 3x3-blocks and some given cells instead of given sums in a given segmentation as in "Killer"-problems ?

(Any answer different from "Feel free to construct Jigsaw-Sudokus" preferred :-)
 

by: aw

 30-Jun-2025, 09:23
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I apologize, forget it - just found www.sudokuwiki.org/Weekly-Jigsaw.aspx.
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by: hepa

 29-Jun-2025, 11:05
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1
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5
 

by: optimator

 29-Jun-2025, 14:06
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 I read your instructions last week, but I am still not understanding the basic rules. Could you please explain? Thanks for your help and the interesting puzzles!
 

by: Ben

 29-Jun-2025, 17:00
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 Are you familiar with the Str8ts B puzzles that Andrew publishes weekly? The basic rules for jigsaw puzzles are exactly the same. The only difference is that the blocks are not 3x3 squares. They are odd shapes. But the 9x9 puzzle is still divided into 9 9-cell blocks, and a block cannot contain the same digit twice.
 

by: optimator

 29-Jun-2025, 17:29
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 thanks, Ben!
 

by: optimator

 29-Jun-2025, 17:33
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 Last week, a 5 was missing from col 6, so A6 black is a 5. This means the block with A6 has no 5 in the other cells? How about B-setti rules?
 

by: Ben

 29-Jun-2025, 20:08
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 No, J-Setti rules are more complex than B-Setti rules.

Even with B-Str8ts you could not make the assumption that the block with A6 has no 5. You would only know that either block 2 or block 5 had no 5, and it would depend on which row was also missing a 5.

With J-Str8ts, in many cases, you can not narrow it down in that way, because of the way the blocks overlap. You would just know that one of the blocks omits a 5.

If a digit is not omitted from any row, then you know that digit appears in all columns and in all blocks. (and vise versa).
If a set number of rows require a digit and the cells in play that contain that digit are spread across the exact same number of blocks, then you know that those blocks require that digit, and that the other cells for those blocks NOT in those rows cannot contain that digit.

So, that last sentence was a mouthful. When I get a chance I will document an example puzzle end-to-end. But it probably won't be this week.
 

by: optimator

 29-Jun-2025, 20:19
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 Oof! I'm not at this level (yet). Thanks, again.
 

by: OneGuess

 30-Jun-2025, 15:15
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1
 2 missing in one box and 3 mandatory required in all boxes (or the other way round just to avoid too much of a spoiler) thereafter, solving this wonderful jigsaw puzzle possible without further chains….
 

by: Auwei

 5-Jul-2025, 15:27
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Needed a chain about cand 2 in col 8.
Again a beautiful developing puzzle, thanks to hepa!
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by: acs
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5
 The Weekly Str8ts puzzle #784
 

by: hp

 29-Jun-2025, 10:42
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 very hard stuff
after many CE, Setti 7 and xwing 2 no progress for me
After E8=8 still a long way, but chainfree
 

by: MrL

 29-Jun-2025, 12:27
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 Like hp above, but instead of E8=8, I decided if E4 or E9 is 7.
 

by: MartinL

 29-Jun-2025, 12:50
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 Trying E8 = 6 leads to a contradiction after a little chain
 

by: MME

 29-Jun-2025, 21:03
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The key for me is the Seti consideration on 8: 8 is a must in at least 8 rows. If there is no 8 in row E, E8=6 and then G1=6 (single in row), so no 8 in column 1 => 8 is a must in columns 2-9. Later, there is a Jellyfish on 3 and the mentioned chain to exclude 6 from E8.
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by: acs
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2
 The Weekly Str8ts B puzzle #176
 

by: Loser

 29-Jun-2025, 10:56
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 tommorow :)
 

by: Neunmalneun

 30-Jun-2025, 13:10
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 Very elegant puzzle. Thanks a lot.
 

by: OneGuess

 1-Jul-2025, 16:33
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 I was close to giving up - lucky guess on E9 made it, finally
 

by: optimator

 1-Jul-2025, 18:44
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 Hard: I used CE on col 1 & 2, but then was stuck. I made a lucky low guess on D3.
 

by: Auwei

 2-Jul-2025, 12:22
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 A UR consideration in GHJ34 gets you going.
Thanks to Andrew, cool level for a hot day
 

by: BP

 2-Jul-2025, 20:21
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Very tough, Made it withiut chains - just. Used the dam UR as Auwei, but that wasn't enough by far. Thank you, Andrew!
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by: acs
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9
 The Weekly Str8ts BX puzzle #176
 

by: WolfgangL

 29-Jun-2025, 00:12
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 Develops very nicely, standard tools only, thanks!
 

by: ThomasF

 29-Jun-2025, 09:28
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 Indeed, very nice, thanks
 

by: Martinus

 29-Jun-2025, 11:20
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 Like the others. Thanks!
 

by: kmr

 29-Jun-2025, 11:39
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 Very nice puzzle, solves smoothly.
 

by: optimator

 29-Jun-2025, 11:51
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 6'
 

by: jgrab

 29-Jun-2025, 15:30
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 25 min; I get used to it ...
 

by: EC

 1-Jul-2025, 09:59
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15 min, one chain
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by: acs
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5
 The Weekly Str8ts X puzzle #176
 

by: optimator

 29-Jun-2025, 12:39
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 I needed chains, settis, and another chain to finish
 

by: BP

 29-Jun-2025, 15:59
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 We solved this one without chains using the following non standard steps:

1 in ADH6 plus Setti 1 => 1 in col 7

UR F7<>58

F67+G7 = 567 => 5 in F6G7

5 in F6G7 plus Setti 5 => 5 in col 7

9 in A1H8 plus Setti 9 => 9 nowhere else in A,H

very skewed xwing: 7 in D4G7 and E46 => G6<>7

Many thanks, Andrew!
 

by: Auwei

 30-Jun-2025, 15:56
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 @BP: what an elegant way!
 

by: OneGuess

 1-Jul-2025, 11:11
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 not elegant, just hard work for me: but assuming 5 in all rows (or not) was enough to solve without further chains.
 

by: Cosmanita

 1-Jul-2025, 18:42
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 Hard, but doable using ideas from BP and many setties: My way: G3=3 not working in \, H8=9 not working in row F and \ plus setties, C6 not 1, UR F7 from BP, both options in G7 result in no 8 in F, I5=7 and E6=7.
 

by: Jan

4-Jul-2025, 19:49
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 My path:
setti 2 (affects rows D and F)
if ABC2 high, B2 must be 7; in that case, no 1 on \ diagonal, so ABC2 low
setti 4 solves H9 and more
setti 6 removes 9 from F789
now 9 in A1H8 and 1 in AH6. As noted by BP, this means all other 9s in rows AH are impossible
if G7=7, F8 also 7 and no 7 left in row D; G7=5 then solves

BP: Can you please explain your UR in F7?
 

by: BP

 4-Jul-2025, 21:44
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@Jan: At that point we had:
ABCD7 = 1234,
F123 = 234,
F678 = 567 or 678,
FGH7 = 567 or 678.
So:
If F7=5 then F68=67, GH7=67, so we could substitute F7=5 by F7=8.
By the same argument F7=8 could be substituted by F7=5.


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  • 0:40:39 nach vielen Versuchen und einmal Raten. Sehr schwer!
    - zoo-pony (Tartlau)
  • hard. only with e8+e1
    - chris1
  • 35' with the hints E8+E1, w/o no chance. Danke!
    - barbara
  • 21 min - without hints, CE and settis
    - Susan
  • 29 min
    - relijo
  • Decision on 6 in E1, then settis. The rest is careful elimination.
    - solver_2
  • 12 min without hints but one lucky guess
    - EC
  • 3rd attempt with chain to find 7 in E.
    - UZ
  • 4th attemp, guess on E6, no hints needed
    - easydoesit
  • stunden, das mit E1 hätte ich nicht gedacht
    - dersoloist
  • 33' with hints
    - Maven
  • 28:30 - excellent balance between challenging, but doable with a few settis and logic, nice one :)
    - pefferlass
  • 35 min - 4. Versuch, Danke hp und susi
    - Rot
  • 9 min with one lucky guess on E1
    - Nessi
  • ~hr: CE, wings, settis, swordfish. Very nice!
    - optimator
  • 15:20. Some settis.
    - Kgal
  • 38 min, a hard one. My way was the same as Susi's.
    - Alex
  • 21' with a chain in J8, no settis
    - Mary
  • 119 min
    - wjanet
  • Difficult, but done. 7's are crusial.
    - MrL
  • 34' Susi's notice helped to a nice one
    - Richard
  • 35' - needed a chain
    - COM
  • 1 h
    - Loser
  • for me only with some chaining on EJ8, then settis
    - ThomasF
  • 53'. Needed one chain. Than just logic. Hard one.
    - MartinL
  • 2.5 h with BCA.
    - E.H.
  • 33 min - start with finding 7 in last row, h/l in column 6 is logic, then carefully elimination. Great one!!!
    - Susi
  • 26 min with guess in E1
    - Beate
  • 33', settis
    - pax
  • 1h32' Logic and settis
    - Manfred
  • 1h; hard work. Needed one chain/contradiction on E8.
    - jgrab