help with 8x8 sudoku

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help with 8x8 sudoku

Postby urhegyi » Tue Dec 29, 2020 10:28 pm

The only possible steps I see are A)UR type 1 R17C48 on 3/8 : R7C4<>8 = 7!
B)xy-wing P=R7C4=7/8 if 7 then R8C1=3; if 8 then R1C4=3 --> R2C1<>3=7!
any other solutions I overview because this puzzle is medium level !!! (I never used an xy-wing in a medium sudoku before; usually they solve with basic steps)
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Re: help with 8x8 sudoku

Postby 999_Springs » Wed Dec 30, 2020 3:46 am

your UR doesn't work because the 4 cells have to be in 2 different boxes and not 4

your xy-wing works and that's how i would have solved the puzzle too. i don't see any easier solutions either as i don't see any basic moves or any single digit patterns. i am guessing the puzzle was either mis-rated or was only called "medium" because the sticking point is so late in the puzzle

there is also a bug+2: r5c4 or r7c7 must be 8 => -8 r7c4
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Re: help with 8x8 sudoku

Postby 1to9only » Tue Mar 02, 2021 8:28 am

For XY-Wings, SE searches for the pivot XY cell from r1c1 to r9c9 order, so finds the other XY-Wing first:
r1c4=3,r2c1=7 or r1c4=8,r7c4=7 => r8c1<>7

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