Aug 16 - Super Hard
Puzzle Copyright © Kevin Stone
Share link – www.brainbashers.com
Reasoning
R5C5 can only be <1>
R5C8 is the only square in row 5 that can be <7>
R8C6 is the only square in row 8 that can be <1>
R5C1 is the only square in column 1 that can be <6>
R5C9 is the only square in column 9 that can be <2>
Squares R1C7 and R3C9 in block 3 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 block.
R2C7 - removing <45> from <13459> leaving <139>
R2C8 - removing <45> from <13459> leaving <139>
R3C8 - removing <45> from <13459> leaving <139>
Squares R3C1 and R7C1 in column 1 and R3C9 and R7C9 in column 9 form a Simple X-Wing pattern on possibility <5>. All other instances of this possibility in rows 3 and 7 can be removed.
R3C2 - removing <5> from <14578> leaving <1478>
R7C2 - removing <5> from <2358> leaving <238>
R3C5 - removing <5> from <345789> leaving <34789>
R7C5 - removing <5> from <589> leaving <89>
R3C6 - removing <5> from <59> leaving <9>
R7C6 - removing <5> from <569> leaving <69>
R7C8 - removing <5> from <3456> leaving <346>
R7C6 can only be <6>
R2C6 can only be <5>
R2C4 is the only square in row 2 that can be <6>
R7C5 is the only square in row 7 that can be <9>
Squares R2C8<139>, R3C8<13>, R4C8<149> and R7C8<34> in column 8 form a comprehensive naked quad. These 4 squares can only contain the 4 possibilities <1349>. Since each of the squares must contain one of the possibilities, they can be eliminated from the other squares in the column.
R6C8 - removing <4> from <456> leaving <56>
R8C8 - removing <3> from <356> leaving <56>
Squares R1C3 and R1C5 in row 1 and R9C3 and R9C5 in row 9 form a Simple X-Wing pattern on possibility <7>. All other instances of this possibility in columns 3 and 5 can be removed.
R3C5 - removing <7> from <3478> leaving <348>
R8C3 - removing <7> from <23578> leaving <2358>
R8C5 - removing <7> from <578> leaving <58>
Squares R6C8, R8C8, R6C7 and R8C7 form a Type-4 Unique Rectangle on <56>.
R6C7 - removing <5> from <456> leaving <46>
R8C7 - removing <5> from <3568> leaving <368>
Squares R3C1 (XY), R3C9 (XZ) and R2C3 (YZ) form an XY-Wing pattern on <4>. All squares that are buddies of both the XZ and YZ squares cannot be <4>.
R3C2 - removing <4> from <1478> leaving <178>
Squares R6C7 (XY), R1C7 (XZ) and R6C8 (YZ) form an XY-Wing pattern on <5>. All squares that are buddies of both the XZ and YZ squares cannot be <5>.
R5C7 - removing <5> from <59> leaving <9>
R2C8 is the only square in row 2 that can be <9>
R4C3 is the only square in row 4 that can be <9>
R4C2 is the only square in row 4 that can be <2>
R7C4 is the only square in row 7 that can be <2>
R8C3 is the only square in row 8 that can be <2>
R6C3 is the only square in column 3 that can be <3>
R6C2 is the only square in block 4 that can be <4>
R6C7 can only be <6>
R6C8 can only be <5>
R8C8 can only be <6>
Intersection of row 7 with block 7. The value <8> only appears in one or more of squares R7C1, R7C2 and R7C3 of row 7. These squares are the ones that intersect with block 7. Thus, the other (non-intersecting) squares of block 7 cannot contain this value.
R8C2 - removing <8> from <3578> leaving <357>
R9C3 - removing <8> from <578> leaving <57>
Squares R3C2 (XYZ), R3C4 (XZ) and R2C2 (YZ) form an XYZ-Wing pattern on <8>. All squares that are buddies of all three squares cannot be <8>.
R3C1 - removing <8> from <58> leaving <5>
R3C9 can only be <4>
R7C1 can only be <8>
R7C9 can only be <5>
R1C7 can only be <5>
R7C2 can only be <3>
R7C8 can only be <4>
R4C8 can only be <1>
R9C7 can only be <8>
R8C7 can only be <3>
R4C7 can only be <4>
R3C8 can only be <3>
R2C7 can only be <1>
R2C2 can only be <8>
R3C5 can only be <8>
R2C3 can only be <4>
R5C2 can only be <5>
R2C5 can only be <3>
R1C3 can only be <7>
R3C4 can only be <7>
R8C5 can only be <5>
R5C3 can only be <8>
R8C2 can only be <7>
R8C4 can only be <8>
R3C2 can only be <1>
R9C3 can only be <5>
R9C5 can only be <7>
R1C5 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 setting.