#672, November 15 - November 21, 2025:
The Weekly 'Unsolvable' Sudoku Puzzle
by Andrew Stuart
|
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: Dieter
#672 - initially populated cells: 24 = 29,6%
No solver used, solver = brain.
basics: G2=A4=B1=7; D6=5
populated cells: 28 = 34,6%
Strategy: Numbers 7,5,3,9 occur most frequently, combine two cells.
combinations of F5 = (1,2,7) and H5 = (1,3,5,6)
1 matrix left after basic checks: F5/H5 = 2/1 solves with A1=1
Optimization:
H5=1 & A1=1 solve.
... by: numpl_npm
Sorry. There's also the possibility ...
{9999} in 5x5 (b1456), {999} in 4x4 (b789)
... by: numpl_npm
39r39c4 14rr57c4 7r1c4 7r7c2 7r2c1 5r4c6
.3.74..9.7..5.1...6.......7...8.5.42..7.9.5..54.6.3...97......3...2.7....1..8..7.
I'm not entirely sure, but
4x4: r1789c1467, 5x5: r23456c23589
{999} in 5x5 (b145), so {99} in 4x4 (b79), 9r9c46, so 9r8c9
Then SE9.1 -> SE8.3
... by: Frans Goosens
#672
Combination 2-digits cells
C4=3 Wrong, Undo calculation
C4=9 No solution, Fixed
C5=2 Wrong, Undo calculation
C5=3 ( D1=3 ) Solved,
Total solving time is : 68 sec.
Number of logical steps is : 7732
... by: Serban
# 672 A4=B1=G2=7 D6=5 Basics to 28
1. Number 2 n=2 e=7 N=26 Nc=19 Ns= => E1=2 basics to 58
---1a. XY-Wing-148 [CG7,B9] => A7 <>8 => G7=8 solve
2. Number 4 n=3 e=6 N=17 Nc=13 Ns=13 => H7=4 solve
3. Number 9 n=3 e=6 N=14 Nc=10 Ns=5 => D7=9 solve
Note: C4=J7=9
