Logic Masters Deutschland e.V.

Dutch Flat Mates: Binary Sum Arrows

(Published on 5. November 2025, 08:00 by damo_89)

It is once again a great pleasure to feature in the long-running Dutch Flat Mates series by Flinty. This week the paired constraint is Binary Sum Arrows. If you'd like other puzzles featuring this constraint, I can recommend the following by its creators:

Rules:

  • Normal sudoku rules apply: Place the digits 1 to 9 once each in every row, column, and 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
  • Binary Sum Arrows: Arrows contain "binary sums". Each cell along the arrow is a bit, starting with the most significant bit and going to the least significant. If a cells contents are odd, that puts a 1 in that bit, and if a cells contents are even, that puts a zero in that bit. The digits in the bulb of the arrow are that sum expressed as a one or two-digit decimal number (read from left-to-right)
    • (For example, a five cell arrow would have a 16's bit, an 8's bit, a 4's bit, a 2's bit, and a 1's bit. Cells with odd odd even even odd along that arrow would then give a binary sum of 16 + 8 + 0 + 0 + 1 = 25)

Play on Sudokupad

Download full solution guide (PDF)

Previous Dutch Flat Mate Puzzles
This has been a weekly series since '18 Oct 23'. Here is a spreadsheet link for all the previous puzzles in the series, which also has a few teasers for upcoming constraints/guest setters in the series (subject to change).

This alternative link offers a limited LMD search for Dutch Flat Mates.

Solution code: Row 5

Last changed on -

Solved by OJPS, spookyripper, alexsmart, sorryimLate, tuturitu, redovermars, Silentdodo, Mozart40, marcmees, Vodakhan , Nada, SKORP17, goodcity, DanishDynamite, fauxturtle, MaxSmartable, biorycbyd, kangaroo, ... teuthida, Jaylove, micsova, palpot, Caswell, MorsBe, Crusader175, SeveNateNine, meiwanmeiliao, butch02, nyxie, Myreque, GorgeousNicko, Shmartus, Selsted, NEWS, steinchen, widjo, deangaudet, Clementi
Full list

Comments

on 7. November 2025, 23:34 by VitP
i got about halfway through, and ran into a brick wall.
did i forget a rule?.

lol

on 7. November 2025, 01:21 by Aronana
Very Nice! Liked the touch of adding in the digits to make the binary easier to read.

on 6. November 2025, 14:09 by Flinty
You've done a wonderful job with this, it's an excellent puzzle. x

on 6. November 2025, 06:40 by gaihou
It gets much easier to solve by parity,love this Sudoku

Last changed on 5. November 2025, 15:29

on 5. November 2025, 08:44 by Mozart40
Sounds like a great constrain to me. But I've no clue how to approach this.

/Edit: Okay two numbers found. Looks like a way to go.

/Edit2: After finding a way to think about it, it was a pleasure. Thx for sharing.

Difficulty:2
Rating:97 %
Solved:59 times
Observed:0 times
ID:000PHQ

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Solution code:

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