#661, August 30 - September 5, 2025:
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).
|
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.
Share and Enjoy
Supporter Members have access to all these puzzles going back to number 1.
Discussion...
Post an idea here...
... by: Frans Goosens
#661
Combination 2-digits cells
A1=2 Wrong, Undo calculation
A1=5 No solution, Fixed
A5=1 Wrong, Undo calculation
A5=2 No solution, Fixed
B1=3 Wrong, Undo calculation
B1=6 No solution, Fixed
B5=3 ( A3=8 ) Solved,
Total solving time is : 90 sec.
Number of logical steps is : 11804
... by: Dieter
#661 - initially populated cells: 22 = 27,2%
No solver used.
basics: %
Strategy: Numbers 3,4,6,8 occur most frequently, combine two cells.
combinations of G3 = (2,6,8) and G5 = (1,3,4,6)
G3/G5 = 6/1 solve.
... by: Serban
# 661 Basics to 22
1. Number 1 n=2 e=7 N=28 Nc=28 Ns=28 => D8=G5=1 solve
Note: F2=C6=A9=1
2. Number 4 n=3 e=6 N=21 Nc=19 Ns=54 =>G1=H9=4 basics to 37
2a. X chain x=1=>[]<>1=> H1=1 solve
3. Number 9 n=2 e=7 N=28 Nc=27 Ns=3 => E9=H7=9 basics to 51
3a. X chain x=2=>[G3,C4,D5,F7]<>2 =>C3=2 solve
