     Sudoku Solution Path   Copyright © Kevin Stone R1C1 is the only square in row 1 that can be <3> R4C6 is the only square in row 4 that can be <4> R4C4 is the only square in row 4 that can be <9> R5C5 is the only square in row 5 that can be <2> R6C1 is the only square in row 6 that can be <2> R8C1 can only be <5> R8C8 can only be <9> R8C2 can only be <2> R8C9 can only be <7> R6C4 is the only square in row 6 that can be <6> R7C3 is the only square in row 7 that can be <9> R3C7 is the only square in column 7 that can be <6> Squares R1C3, R1C4 and R1C6 in row 1 form a simple locked triplet. These 3 squares all contain the 3 possibilities <157>. Since each of the squares must contain one of the possibilities, they can be eliminated from the other squares in the row.    R1C7 - removing <1> from <128> leaving <28>    R1C8 - removing <15> from <158> leaving <8>    R1C9 - removing <15> from <124589> leaving <2489> R1C7 can only be <2> R9C9 is the only square in row 9 that can be <2> Squares R7C1 and R9C3 in block 7 form a simple locked pair. These 2 squares both contain the 2 possibilities <18>. Since each of the squares must contain one of the possibilities, they can be eliminated from the other squares in the block.    R9C1 - removing <18> from <1468> leaving <46> Intersection of row 2 with block 3. The value <5> 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.    R3C9 - removing <5> from <145> leaving <14> Intersection of block 2 with row 1. The value <1> only appears in one or more of squares R1C4, R1C5 and R1C6 of block 2. These squares are the ones that intersect with row 1. Thus, the other (non-intersecting) squares of row 1 cannot contain this value.    R1C3 - removing <1> from <157> leaving <57> Squares R5C6 and R5C7 in row 5 and R9C6 and R9C7 in row 9 form a Simple X-Wing pattern on possibility <3>. All other instances of this possibility in columns 6 and 7 can be removed.    R7C7 - removing <3> from <138> leaving <18> Squares R7C1 and R7C7 in row 7 form a simple locked pair. These 2 squares both contain the 2 possibilities <18>. Since each of the squares must contain one of the possibilities, they can be eliminated from the other squares in the row.    R7C9 - removing <18> from <1358> leaving <35> Intersection of column 9 with block 6. The value <8> only appears in one or more of squares R4C9, R5C9 and R6C9 of column 9. These squares are the ones that intersect with block 6. Thus, the other (non-intersecting) squares of block 6 cannot contain this value.    R5C7 - removing <8> from <138> leaving <13> R5C3 is the only square in row 5 that can be <8> R9C3 can only be <1> R4C1 can only be <7> R9C8 can only be <5> R7C1 can only be <8> R9C4 can only be <7> R2C8 can only be <1> R7C9 can only be <3> R2C1 can only be <6> R3C9 can only be <4> R1C9 can only be <9> R3C1 can only be <1> R7C7 can only be <1> R5C7 can only be <3> R7C5 can only be <5> R4C9 can only be <8> R9C7 can only be <8> R9C6 can only be <3> R5C4 can only be <1> R1C2 can only be <4> R2C9 can only be <5> R2C2 can only be <9> R9C1 can only be <4> R4C5 can only be <3> R6C9 can only be <1> R5C6 can only be <7> R1C4 can only be <5> R6C6 can only be <5> R6C5 can only be <8> R1C6 can only be <1> R3C5 can only be <7> R9C2 can only be <6> R1C3 can only be <7> R3C3 can only be <5> [Puzzle Code = Sudoku-20190916-VeryHard-302732]    