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#820, March 8 - March 14:
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.
All Access Supporters can load all puzzles from number 1.
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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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No full solutions please!

by: hepa

 8-Mar-2026, 11:13
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by: Only Human

 8-Mar-2026, 14:38
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 had to use a few short chains - wonderful puzzle, again, thank you hepa
 

by: aw

 9-Mar-2026, 11:23
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 Gee - the first time I solved hepa's Jigsaw before the rest of the set :-)
Thanks a lot!
 

by: kris

 9-Mar-2026, 14:34
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 Very nice! Needed a micro chain at the end.
 

by: Auwei

 9-Mar-2026, 15:05
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 Once more: just beautiful, thanks to hepa!
 

by: Harm

 10-Mar-2026, 17:54
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 Can someone explain to me how the black squares relate to the rows and columns covered by the puzzle pieces? Or is there no connection, and the black squares correspond to any missing numbers anywhere on the board? Thank you very much for your answer.
 

by: hepa

 10-Mar-2026, 18:51
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 @harm: Please see "How to Play Str8ts" on top left on this page
 

by: Harm

 10-Mar-2026, 19:25
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 Thank you, hepa, for your quick reply and the challenging puzzle.
Perhaps I didn't express myself clearly. I solved the puzzle, but only after I stopped worrying about the immediate influence of the black squares. So either D1 or E1 is a 3 that is missing in this part. However, the 3 is missing in row F and column 7, while the puzzle piece in which the 3 is missing does not contain this row/column. So it seems that the location of the missing numbers has nothing to do with their location on the board (unlike in the other STR8ts variations, right?
 

by: hoke

 11-Mar-2026, 10:02
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 The jigsaw must have at least one field in the row and one in the col where the same number is missing, i think.
 

by: hepa

 11-Mar-2026, 11:21
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 @Harm: I assume you are familiar with B-Str8ts Strategies -> B-Setti's rules.
Rule I is also true for Jigsaw Str8ts.
Rule II and III can only be applied if the number of rows equals the number of boxes they intersect (same for columns).
So for many Jigsaw-Str8ts box shapes this cannot be used.
But there are some shapes where application is possible, e.g. www.sudokuwiki.org/Jigsaw_Shape_List -> Tim Tang
- boxes 1,5 columns 1,2
- boxes 2,4,6,7,8 columns 3,4,5,6,7
- boxes 3,9 columns 8,9
I hope this answers your question.
 

by: hoke

 12-Mar-2026, 14:37
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 So it seems, that my assumption was complete nonsense, sorry for that. Strange,that it helped me in the past.
 

by: Ben

 12-Mar-2026, 16:55
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@hoke, it's an assumption I made in the early days of Jigsaw's. And yes, it "helped", until I found a puzzle where it led me astray.

Because of this, it is important to consider jigsaw boxes where you know which digits are required, so;
- if a box has no black cells
- the number of black cells equals the number of candidates that are definitely missing
- the box contains a naked set of digits

Those known candidates can help you apply important eliminations in other boxes.
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by: acs
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 The Weekly Str8ts B puzzle #212
 

by: optimator

 9-Mar-2026, 05:37
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 1' finally one I can do this week.
 

by: EC

 9-Mar-2026, 20:44
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logicaly done in a few minutes
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by: acs
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 The Weekly Str8ts puzzle #820
 

by: Jan

 10-Mar-2026, 13:08
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 It took me a longish chain to eliminate the last 1 in row D and thus decide high/low in the upper left corner. After two obvious 3-wings, the decisive move was to consider the effect of G8=2 on G2, as it allows you to eliminate a digit from that cell. After that, two more obvious x-wings complete the puzzle.
 

by: Gerd

 10-Mar-2026, 21:26
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 How can row D live without 1?
 

by: Rudik

 11-Mar-2026, 17:24
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 Yes - how can row D live without it, I wonder?
sometimes it's really amazing what nonsense one can read here.
 

by: Jan

 11-Mar-2026, 19:39
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 Just think instead of wondering...eliminating 1 in that row disproves the alternative being pursued and proves the other.
 

by: Gerd

 11-Mar-2026, 21:08
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 ??
 

by: Jens

 12-Mar-2026, 08:21
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 Hi Jan - pls check:
1. puzzle #820 ? If yes, than
2. row number D has one Black Cell, filled with 9, or perhaps column number 4 with one empty Black Cell?
 

by: David

 12-Mar-2026, 18:35
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Jan did a prove by contradiction:
He has two options A and B. He assumes A is correct. This assumption leads to the fact, that all 1s are eliminated from row D. This proves A is incorrect and therefore B has to be correct.
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by: acs
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 The Weekly Str8ts BX puzzle #212
 

by: Ollie

 8-Mar-2026, 14:35
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 Way too hard for me. Needed 5 long chains :-(
 

by: optimator

 8-Mar-2026, 14:46
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 twice I've gotten to a point where I don't get a solution but I can't see my mistake
 

by: AndreasM

 9-Mar-2026, 10:43
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 Essentially, the puzzle is about the ranges in column 7. After, admittedly, some work both options lead to the same digit in A3. Then you've got something to work with. The puzzle is interesting without being frustrating. Thank you!
 

by: kris

 9-Mar-2026, 15:29
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 @AndreasM: Solving ranges of column 7 is quite easy: In box 6 and so in column 7 (box setti) there must be missing exactly 2 digits of 6789. That allows only one single combination on GHJ7 and clears all ranges. However after that I find it still very demanding and don't see a chainless way.
 

by: AndreasM

 9-Mar-2026, 16:49
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@kris: Digits 8 and 9 missing in box 6 was easy to verify, agreed. But in order to make inferences on column 7 you need information on box 3 which I didn't have at an early stage. As to chains, I find this concept slightly doubtful, if applied to BX-puzzles. The richness of the BX-rules allows to draw far-reaching conclusions based on very few assumptions. Of course, you may call this chains, even if there are comparatively few steps involved. The complexity of BX-puzzle solving stems from the broadness of possible inferences, not from their depth.
And yes, the puzzle is not exactly easy.
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by: acs
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 The Weekly Str8ts X puzzle #212
 

by: Only Human

 8-Mar-2026, 08:28
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 solved with a few headchains - wonderful X puzzle (again)
 

by: aw

 12-Mar-2026, 10:32
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 Solved in the end, but with too many chains and too much trial and error to be fun - finally a lucky guess on E6 and no desire anymore to falsify the alternative ...
 

by: OneGuess

 13-Mar-2026, 12:08
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B8= single 7, only 2 options remaining for 8 in column 9 (E9 cannot be8) and if you go for B9 all falls in place with CE
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Page created on 27-June-2010.
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  • 90min
    - JulioFlor
  • @barbara: to avoid any misunderstanding - A89 does not mean that A89 = 89.
    - marianne
  • @Marianne: Danke! Tomorrow I will try once more.
    - barbara
  • @barbara: you are right with A89 and HJ9.
    - marianne
  • @dersoloist: Danke! Aber immer noch zu vielseitig. Werde viell. noch mal versuchen.
    - barbara
  • ABC 1, ist hoch A2 ist dann die 2 oder die 9.
    - dersoloist
  • @ - denk_mal: Danke! Yes , so I have. And FGHJ with 9 and 8, or with 5, maybe 4 too?
    - barbara
  • D7 is 1
    - denk_mal
  • Please, help - (Die Kirschen hängen sehr hoch). Row A 89 is 34, HJ 9 is 12? And where's the 1 in Row D?
    - barbara
  • I am stuck too, to many guesses, no logic... Not a nice one.
    - Mouche
  • I am stuck. Any help?
    - easydesit
  • Lucky success, finally.
    - jgrab
  • Solved at 2nd attempt after h/l-decision in col. 1 with some settis and fish.
    - UZ
  • Schwer! Lang! Zuerst mal A1-A5 l/h versucht, einer der beiden führt recht bald zum Widerspruch. Noch weitere Versuche benötigt.
    - b*k*
  • @Eumel -> Beate made decisions in col 1.
    - Jens
  • 41 min im 5. Versuch - ich fand es schwer
    - Rot
  • 30 min
    - relijo
  • 3 tries, keep running into errors...
    - martijn
  • Needed HC. No solver, no hint.
    - H.E.
  • der Solist, nicht Walt, sorry
    - biggi
  • @walt: auf keinen Fall,danke ;-)
    - biggi
  • habs gelöst, bitte die A4 nicht verraten
    - dersoloist
  • kann das sein, dass A4 die 8 ist?
    - dersoloist
  • 1.5 hr with 2 long chains
    - Maven
  • A hint like "make a desicion in XY" is not a hint.
    - Fred
  • solved. but not amused
    - chris1
  • 33 min - one guess, then smooth sailing
    - Stef
  • Sehr schwer, A4 war der Schlüssel, dann viele x-wings und settis.
    - S. Walt
  • Was ist denn Beates Tipp?
    - Eumel
  • 45 min. Like Beate. Too much guessing/HC. X wings on 3s and 7s help but do not solve.
    - Cleo
  • @Beate Thanks for your tipp.
    - Jens
  • 28 min on maybe 4th attempt... started with Alex' hint and had to made a choice in F1 later on. Nice puzzle, but too hard for me.
    - Beate
  • 1:34 h; really hard one, but nice
    - Nessie
  • 68' - needed several chain, did not find a "logic" solution
    - COM
  • 29 min, hi-lo decision in col. 1 did it for me
    - Alex
  • 42 min, a hard nut, but solvable by standard tools
    - fred
  • 1:08 - wow, a really 5☆, lot of fun :)
    - Susi
  • 1:20h, what a challenge. VCE in upper left corner
    - flowerwaffle
  • 34', nice for of lazy sunday morning :-)
    - MartinL
  • 1:02:11 nicht ganz leicht
    - zoo-pony (Tartlau)
  • 18 min - a real challenge, nice
    - Nessi
  • Hi/Lo decision on column 1, settis and careful elimination.
    - Solver_4
  • 45', one chain
    - AB Traherne
  • 55' early morning
    - pax