The full reasoning can be found below the Sudoku.
Mar 05 - Hard
Puzzle Copyright © Kevin Stone
Reasoning
R3C8 is the only square in row 3 that can be <1>
R3C4 is the only square in row 3 that can be <6>
R6C4 is the only square in row 6 that can be <1>
R6C2 is the only square in row 6 that can be <6>
R9C5 is the only square in row 9 that can be <1>
R9C1 is the only square in column 1 that can be <6>
R3C6 is the only square in column 6 that can be <9>
R2C2 is the only square in column 2 that can be <9>
R7C6 is the only square in column 6 that can be <8>
Squares R2C7 and R2C8 in row 2 form a simple naked pair. These 2 squares both contain the 2 possibilities <47>. Since each of the squares must contain one of the possibilities, they can be eliminated from the other squares in the row.
R2C1 - removing <47> from <2457> leaving <25>
R2C5 - removing <4> from <2458> leaving <258>
R2C9 - removing <47> from <478> leaving <8>
Squares R2C7 and R2C8 in block 3 form a simple naked pair. These 2 squares both contain the 2 possibilities <47>. Since each of the squares must contain one of the possibilities, they can be eliminated from the other squares in the block.
R1C7 - removing <4> from <3469> leaving <369>
R1C8 - removing <4> from <349> leaving <39>
R1C9 - removing <4> from <3469> leaving <369>
Intersection of row 3 with block 1. The values <37> only appears in one or more of squares R3C1, R3C2 and R3C3 of row 3. These squares are the ones that intersect with block 1. Thus, the other (non-intersecting) squares of block 1 cannot contain these values.
R1C1 - removing <3> from <2345> leaving <245>
R1C3 - removing <3> from <23458> leaving <2458>
Intersection of row 6 with block 6. The value <4> only appears in one or more of squares R6C7, R6C8 and R6C9 of row 6. These squares are the ones that intersect with block 6. Thus, the other (non-intersecting) squares of block 6 cannot contain this value.
R5C9 - removing <4> from <479> leaving <79>
Intersection of column 2 with block 7. The values <25> only appears in one or more of squares R7C2, R8C2 and R9C2 of column 2. These squares are the ones that intersect with block 7. Thus, the other (non-intersecting) squares of block 7 cannot contain these values.
R8C1 - removing <5> from <3457> leaving <347>
R8C3 - removing <5> from <34578> leaving <3478>
R9C3 - removing <25> from <23457> leaving <347>
Intersection of column 6 with block 5. The value <2> only appears in one or more of squares R4C6, R5C6 and R6C6 of column 6. These squares are the ones that intersect with block 5. Thus, the other (non-intersecting) squares of block 5 cannot contain this value.
R5C5 - removing <2> from <2457> leaving <457>
Intersection of block 5 with row 5. The values <47> only appears in one or more of squares R5C4, R5C5 and R5C6 of block 5. These squares are the ones that intersect with row 5. Thus, the other (non-intersecting) squares of row 5 cannot contain these values.
R5C1 - removing <7> from <2579> leaving <259>
R5C9 - removing <7> from <79> leaving <9>
R4C1 is the only square in row 4 that can be <9>
R8C8 is the only square in row 8 that can be <9>
R1C8 can only be <3>
R1C9 can only be <6>
R1C7 can only be <9>
R4C7 is the only square in row 4 that can be <3>
R7C7 is the only square in row 7 that can be <6>
Squares R2C1 and R5C1 in column 1 form a simple naked pair. These 2 squares both contain the 2 possibilities <25>. Since each of the squares must contain one of the possibilities, they can be eliminated from the other squares in the column.
R1C1 - removing <25> from <245> leaving <4>
R1C4 can only be <5>
R2C5 can only be <2>
R2C1 can only be <5>
R1C5 can only be <8>
R1C3 can only be <2>
R3C5 can only be <4>
R5C1 can only be <2>
R6C3 can only be <7>
R6C9 can only be <4>
R4C3 can only be <5>
R6C7 can only be <2>
R4C6 can only be <2>
R4C8 can only be <7>
R2C8 can only be <4>
R2C7 can only be <7>
R7C8 can only be <2>
R9C7 can only be <4>
R9C3 can only be <3>
R9C6 can only be <5>
R3C3 can only be <8>
R8C1 can only be <7>
R9C9 can only be <7>
R5C6 can only be <4>
R9C2 can only be <2>
R3C2 can only be <7>
R8C3 can only be <4>
R5C4 can only be <7>
R8C5 can only be <3>
R3C1 can only be <3>
R7C2 can only be <5>
R8C9 can only be <5>
R7C5 can only be <7>
R8C2 can only be <8>
R7C9 can only be <3>
R5C5 can only be <5>
R7C4 can only be <4>
Today's Sudoku Puzzles
All daily items change at midnight GMT. set time zone