Logic Masters Deutschland e.V.

Dutch Flat Mates: First Seen Odd/Even

(Published on 14. May 2025, 11:30 by Flinty)

Previous Dutch Flat Mate Puzzles - New Spreadsheet!
This has been a weekly series since '18 Oct 23', please see this new shiny link, listing all the previous puzzles in the series! It also has a few spoilers for upcoming constraints/guest setters in the series (subject to change).

This alternative link offers an LMD search for Dutch Flat Mates.

To play the puzzle, please click the image:

Puzzle Link

Initial Setter Difficulty: 2.5-3 / 5

Normal Sudoku rules apply
Place the digits 1-9 so that they do not repeat in any row, column, or 3x3 box.

Dutch Flats
Every 5 in the grid must have a '1' directly above it or a '9' directly below it. It may have both, but it doesn't need both.

First Seen Odd/Even
Clues outside of the grid tell you the first odd or first even digit seen in that row or column, looking from the direction where the clue appears.
For example, Row 4 could have any number of leading odd digits, but the leftmost even digit must be a 2.

Hint to start

Tracking parity is handy, you only have so many even digit buffers available and can quickly limit a tonne of 5s.

Special Thanks
I believe this is an old constraint, but the GAS series, and particularly the setter Clover brought my attention to it. The 3rd November 24 entry (YouTube link) is a First Seen Odd/Even, but there might be more!

Next Week
Updating the master list of previous Dutch Flat Mates puzzles (see link at the top) only confirmed what I knew about how important this setter was in the longevity of this series, and we've paired parity puzzles back to back, with GoodCity providing something tasty next week!

Solution code: Digits from Row 1

Last changed on -

Solved by Bjd, marcmees, damo_89, ppdswiss, Aaravos18, Arlandro, sorryimLate, sujoyku, dumediat, TVDK, Malakree, palpot, olliwright, da-hans, goodcity, ananth, achim-t, SKORP17, tuturitu, farodin64, ... THef of Time, PippoForte, steinchen, KirkFox, Sus, Askloomok, NEWS, robokong, Yiab, joelth, Joyofrandomness, GorgeousNicko, Frank Puzzles, JoBerlin, marcnesium_iv, yusuf17, jsxft, sedici
Full list

Comments

Last changed on 1. August 2025, 18:40

on 1. August 2025, 18:38 by yusuf17
Great puzzle, but very hard.

@damo_89 I only started pencil marking half way through. Maybe I should have started by fully pencilmarking every cell and then chip them off.

on 14. May 2025, 18:47 by wuc
2.5* to me too. Refreshing rules. Great flow. Thx.

on 14. May 2025, 16:40 by goodcity
What a lovely break in !

on 14. May 2025, 16:08 by da-hans
Very nice puzzle. I found it quite approachable. Agree with the 2.5*

on 14. May 2025, 15:37 by palpot
Fantastic puzzle! I had a lot of fun solving it - really satisfying!

Last changed on 14. May 2025, 14:44

on 14. May 2025, 13:39 by ppdswiss
Dutch Flat Mate rules are great but I defy anyone to complete one without speaking out loud something like "That CAN'T be a 5 because there's no 1 above it or 9 below it!"
I also think it is quite easy in these puzzles to miss a rule and then go quite deep into solving before realising a mistake must have been made. For that reason, giving this a 4* difficulty
Great puzzle though

Flinty: Thank you :)

Last changed on 14. May 2025, 14:43

on 14. May 2025, 13:06 by damo_89
1/5 easy dubz if you pay attention to your own pencilmarks.

Flinty: Maybe even half a star? - lol

Difficulty:3
Rating:95 %
Solved:74 times
Observed:5 times
ID:000NB8

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Solution code:

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