... by: BGH
I was able to verify Dieter & Yves solutions for #665BUT I did not see any "method" so "trial & error?"
In my solutions there's one 2 choices per step. One leads to contradictions, the other leads to the solution.
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#665, September 27 - October 3, 2025:
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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). |
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Discussion...
Post an idea here...Thursday 2-Oct-2025
BUT I did not see any "method" so "trial & error?"
In my solutions there's one 2 choices per step. One leads to contradictions, the other leads to the solution.
Thursday 2-Oct-2025
... by: BGH
3 Step Solution for #6653 @ D8 Row Unit Pair 35.8%
1 @ C4 Cell Pair & Block Unit Pair 56.8%
6 @ F5 Cell Pair & Block Unit Pair 100%
Tuesday 30-Sep-2025
... by: Serban
# 665 Basics to 231. Number 8 n=3 e=6 N=20 Nc=14 Ns=13 => A8=8 basics to 50
1a.X chain x=1 => [E2,H28]<>1; x=4 =>[E29,J3]<>4 => E2=5 OR D3=4 solve
1b. any[A2,E1,F8,H7,J3]=1 solve
1c. any[D6,E8,H5,J2]=2 solve
1d. any[D8,F2,G1]=3 solve
1e. any[D3,E7,H4,J9]=4 solve
1f. any[E2,D7,F6,J3]=5 solve
1g. any[E9,J8]=6 solve
1h. any[E5,F3,H1,J6]=7 solve
1i. any[A3,D1,G2]=9 solve
Tuesday 30-Sep-2025
... by: Yves
A8=8 & E5=7 SolveMonday 29-Sep-2025
... by: Frans Goosens
#665With trial and error
Combination A6=167 and D7=245
************************************************************
A6=1 D7=2 Wrong, Undo calculation
All reset to initial position
************************************************************
A6=1 D7=4 Wrong, Undo calculation
All reset to initial position
************************************************************
A6=1 D7=5 Wrong, Undo calculation
All reset to initial position
************************************************************
A6=6 D7=2 Wrong, Undo calculation
All reset to initial position
************************************************************
A6=6 D7=4 Wrong, Undo calculation
All reset to initial position
************************************************************
A6=6 D7=5 ( I9= ) Solved,
Total solving time is : 59 sec.
Number of logical steps is : 10282
Saturday 27-Sep-2025
... by: Dieter
#665 - initially populated cells: 24 = 29,6%No solver used.
basics: %
Strategy: Numbers 2,3,6,8,9 occur most frequently, combine two cells.
combinations of A5 = (3,6,7,8) and E5 = (2,6,7)
A5=3 & E5=7 solve.
Saturday 27-Sep-2025
... by: Serban
# 665 Basics to 231. Number 3 n=3 e=6 N=19 Nc=12 Ns=10 => G1=C9=3 OR G1=A5=3 basics to 50
1a. X chain x=9 => H2<>9; => H2=4 solve
2. Number 6 n=3 e=6 N=19 Nc=16 Ns=6 =>
2a. E9= F5=6 solve
2b. E9= H3=6 solve
3. Number 9 n=3 e=6 N=21 Nc=16 Ns=8 => A3=E4=9 OR A3=D1=9 solve
Note : H9=9