The full reasoning can be found below the Sudoku.
Apr 27 - Very Hard
Puzzle Copyright © Kevin Stone
Share link:
Reasoning
R1C1 can only be <2>
R1C9 can only be <4>
R2C6 can only be <4>
R5C3 can only be <5>
R1C8 can only be <3>
R4C6 can only be <5>
R8C6 can only be <8>
R6C6 can only be <3>
R5C6 can only be <2>
R1C2 can only be <9>
R2C2 is the only square in row 2 that can be <3>
R2C3 is the only square in row 2 that can be <7>
R4C5 is the only square in row 4 that can be <7>
R4C4 is the only square in row 4 that can be <9>
R2C4 can only be <1>
R3C5 can only be <9>
R2C7 is the only square in row 2 that can be <9>
R5C4 is the only square in row 5 that can be <8>
R6C8 is the only square in row 6 that can be <5>
R8C3 is the only square in row 8 that can be <9>
Squares R4C2 and R6C2 in column 2 form a simple naked pair. These 2 squares both contain the 2 possibilities <14>. Since each of the squares must contain one of the possibilities, they can be eliminated from the other squares in the column.
R8C2 - removing <1> from <1257> leaving <257>
R9C2 - removing <1> from <128> leaving <28>
Intersection of row 2 with block 3. The value <8> only appears in one or more of squares R2C7, R2C8 and R2C9 of row 2. These squares are the ones that intersect with block 3. Thus, the other (non-intersecting) squares of block 3 cannot contain this value.
R3C8 - removing <8> from <168> leaving <16>
Intersection of column 9 with block 9. The value <1> only appears in one or more of squares R7C9, R8C9 and R9C9 of column 9. These squares are the ones that intersect with block 9. Thus, the other (non-intersecting) squares of block 9 cannot contain this value.
R8C7 - removing <1> from <1456> leaving <456>
R8C8 - removing <1> from <12467> leaving <2467>
R9C8 - removing <1> from <1268> leaving <268>
Squares R8C1<156>, R8C4<46>, R8C7<456> and R8C9<15> in row 8 form a comprehensive naked quad. These 4 squares can only contain the 4 possibilities <1456>. Since each of the squares must contain one of the possibilities, they can be eliminated from the other squares in the row.
R8C2 - removing <5> from <257> leaving <27>
R8C8 - removing <46> from <2467> leaving <27>
Squares R3C2 and R3C7 in row 3 and R7C2 and R7C7 in row 7 form a Simple X-Wing pattern on possibility <5>. All other instances of this possibility in columns 2 and 7 can be removed.
R8C7 - removing <5> from <456> leaving <46>
Squares R8C4 and R8C7 in row 8 form a simple naked pair. These 2 squares both contain the 2 possibilities <46>. Since each of the squares must contain one of the possibilities, they can be eliminated from the other squares in the row.
R8C1 - removing <6> from <156> leaving <15>
Squares R2C1 and R2C8 in row 2 and R9C1 and R9C8 in row 9 form a Simple X-Wing pattern on possibility <6>. All other instances of this possibility in columns 1 and 8 can be removed.
R3C8 - removing <6> from <16> leaving <1>
R7C8 - removing <6> from <4678> leaving <478>
R4C8 can only be <4>
R4C2 can only be <1>
R5C7 can only be <1>
R5C5 can only be <4>
R6C2 can only be <4>
R7C5 can only be <6>
R6C4 can only be <6>
R6C5 can only be <1>
R8C4 can only be <4>
R7C3 can only be <8>
R8C7 can only be <6>
R3C7 can only be <5>
R3C2 can only be <8>
R7C7 can only be <4>
R2C9 can only be <8>
R7C8 can only be <7>
R3C3 can only be <6>
R9C2 can only be <2>
R7C2 can only be <5>
R8C8 can only be <2>
R8C2 can only be <7>
R9C8 can only be <8>
R9C9 can only be <1>
R2C8 can only be <6>
R9C1 can only be <6>
R8C9 can only be <5>
R2C1 can only be <5>
R8C1 can only be <1>
Today's Sudoku Puzzles
All daily items change at midnight GMT – set your local time zone.
Note: BrainBashers has a Dark Mode option – I recommend not using your browser's dark mode or extensions for BrainBashers