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#720, October 17 - October 23, 2026:
The Weekly 'Unsolvable' Sudoku Puzzle

by Richard Kröger, guest compiler
WARNING: This is the Weekly 'Unsolvable' Sudoku, rated above 'Extreme'.
This is currently unsolvable by my solver, except perhaps with trial and error strategies.
Using the solver will not help you. (much).

Changes March 2026

Due to the introduction of Forcing Nets many Weekly Unsolvable puzzles can now be solved. I have flagged all the Sudoku ones which are solvable. I am struggling to make any new ones so we'll have to see if the Weekly can continue. The point of the Weekly was to provoke discussion and new ideas, so that is progress. But my solution is unlikely to be optimal so alternatives are welcome.

Archive

Each week a new 'unsolvable' will be published and the previous will be accessible here from this archive section. If you like very tough puzzles, these are for you.
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Supporter Members have access to all these puzzles going back to number 1.

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Saturday 17-Oct-2026

... by: Norman Powell

AS's Solver:
1) Singles G6=9
2) Pointing Pair: eliminate 8F1, 8F3
3) X-Cycles: 3D1
Forcing Networks 4) 6F6, 5) 6E2, 6) 4E2, 7) 4E3
Runs out of strategies.
My Solver: Solution found in fourth pass of Forcing Networks.
Hidden Single G6=9 [AS#1]
Value 8 is confined to Row E and Box 4, eliminate 8F1 and 8F3 [AS#2]
Finned Swordfish: Value 3, CDH347 with Fin F3 - Eliminate 3D1 [AS#3]
[Finned Swordfish is earlier in my list of strategies, as it is simpler and faster than X-Cycles]
Forcing Networks First Pass: 2D1, 4E2 [AS#6], 4E3 [AS#7], 6F6 [AS#4], 7J9,.
Forcing Networks Second Pass: 6E2 [AS#5], 4G1, 4J6
Forcing Network Third Pass: 4A3, 6D1, 2D2, 6D2, 1D6, 6D6, 6E1, 6E3, 2E4, 7G4, 6H4, 6H6
Solved Cell D6=2
Hidden Singles J6=6, G4=5
Forcing Networks Fourth Pass finds solution while testing 7A1 for ON.
Solver VBA for Excel 1 min 4 seconds
Page created on 03-May-2011, last modified on 30-May-2024.
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