Feb 13 - Super Hard
Puzzle Copyright © Kevin Stone
Share link:
Reasoning
R2C3 can only be <7>
R9C3 can only be <2>
R9C2 can only be <1>
R7C2 can only be <4>
R7C1 can only be <9>
R4C6 is the only square in row 4 that can be <7>
R5C9 is the only square in row 5 that can be <4>
R4C3 is the only square in row 4 that can be <4>
R6C8 is the only square in row 6 that can be <7>
R6C1 is the only square in row 6 that can be <8>
R3C2 is the only square in row 3 that can be <8>
R2C2 can only be <5>
R2C6 can only be <1>
R2C5 can only be <9>
R2C4 can only be <8>
R6C4 is the only square in row 6 that can be <1>
R7C5 is the only square in row 7 that can be <7>
R4C1 is the only square in column 1 that can be <5>
R8C5 is the only square in column 5 that can be <1>
Intersection of column 8 with block 9. The values <26> only appears in one or more of squares R7C8, R8C8 and R9C8 of column 8. These squares are the ones that intersect with block 9. Thus, the other (non-intersecting) squares of block 9 cannot contain these values.
R7C7 - removing <6> from <16> leaving <1>
R7C9 - removing <2> from <123> leaving <13>
R7C9 can only be <3>
R1C1 is the only square in row 1 that can be <1>
R3C9 is the only square in row 3 that can be <1>
R3C8 is the only square in row 3 that can be <9>
Squares R1C7 and R1C8 in row 1 form a simple naked pair. These 2 squares both contain the 2 possibilities <45>. Since each of the squares must contain one of the possibilities, they can be eliminated from the other squares in the row.
R1C5 - removing <5> from <2356> leaving <236>
R1C6 - removing <5> from <2356> leaving <236>
Intersection of row 1 with block 2. The value <6> only appears in one or more of squares R1C4, R1C5 and R1C6 of row 1. These squares are the ones that intersect with block 2. Thus, the other (non-intersecting) squares of block 2 cannot contain this value.
R3C5 - removing <6> from <2356> leaving <235>
R3C6 - removing <6> from <2356> leaving <235>
Squares R1C7, R1C8, R8C7 and R8C8 form a Type-3 Unique Rectangle on <45>. Upon close inspection, it is clear that:
(R8C7 or R8C8)<29> and R8C4<29> form a naked pair on <29> in row 8. No other squares in the row can contain these possibilities
R8C6 - removing <2> from <25> leaving <5>
R3C5 is the only square in row 3 that can be <5>
Intersection of block 8 with column 4. The values <29> only appears in one or more of squares R7C4, R8C4 and R9C4 of block 8. These squares are the ones that intersect with column 4. Thus, the other (non-intersecting) squares of column 4 cannot contain these values.
R4C4 - removing <2> from <236> leaving <36>
Squares R3C3 and R3C6 in row 3 and R6C3 and R6C6 in row 6 form a Simple X-Wing pattern on possibility <3>. All other instances of this possibility in columns 3 and 6 can be removed.
R1C6 - removing <3> from <236> leaving <26>
Squares R4C2 (XY), R5C1 (XZ) and R4C4 (YZ) form an XY-Wing pattern on <6>. All squares that are buddies of both the XZ and YZ squares cannot be <6>.
R5C5 - removing <6> from <26> leaving <2>
R5C1 can only be <6>
R3C1 can only be <2>
R6C3 can only be <3>
R6C6 can only be <6>
R3C3 can only be <6>
R4C2 can only be <2>
R6C7 can only be <5>
R1C6 can only be <2>
R4C4 can only be <3>
R6C9 can only be <2>
R1C7 can only be <4>
R4C9 can only be <9>
R1C2 can only be <3>
R3C6 can only be <3>
R1C8 can only be <5>
R8C7 can only be <9>
R9C8 can only be <6>
R1C5 can only be <6>
R4C7 can only be <6>
R9C9 can only be <5>
R8C4 can only be <2>
R9C4 can only be <9>
R9C5 can only be <3>
R7C8 can only be <2>
R7C4 can only be <6>
R8C8 can only be <4>
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