Sudoku Solution Path    Copyright © Kevin Stone R6C4 can only be <8> R1C7 is the only square in row 1 that can be <1> R3C1 is the only square in row 3 that can be <5> R5C9 is the only square in row 5 that can be <1> R6C3 is the only square in row 6 that can be <1> R6C7 is the only square in row 6 that can be <2> R8C7 is the only square in row 8 that can be <5> R8C9 is the only square in row 8 that can be <6> R4C5 is the only square in row 4 that can be <6> R6C5 can only be <4> R3C6 is the only square in row 3 that can be <4> R9C2 is the only square in row 9 that can be <5> R7C4 is the only square in row 7 that can be <5> R9C5 is the only square in row 9 that can be <2> R1C4 is the only square in row 1 that can be <2> R2C9 is the only square in row 2 that can be <2> R7C2 is the only square in row 7 that can be <2> Squares R2C4 and R3C4 in block 2 form a simple locked pair. These 2 squares both contain the 2 possibilities <39>. Since each of the squares must contain one of the possibilities, they can be eliminated from the other squares in the block.    R1C5 - removing <39> from <3789> leaving <78>    R3C5 - removing <39> from <3789> leaving <78> R5C5 is the only square in column 5 that can be <9> R5C2 can only be <4> R4C6 can only be <3> R5C1 can only be <6> R5C8 can only be <3> R6C1 can only be <7> R6C8 can only be <6> R7C5 is the only square in column 5 that can be <3> Intersection of row 1 with block 1. The values <34> only appears in one or more of squares R1C1, R1C2 and R1C3 of row 1. These squares are the ones that intersect with block 1. Thus, the other (non-intersecting) squares of block 1 cannot contain these values.    R2C1 - removing <3> from <389> leaving <89>    R2C3 - removing <3> from <3789> leaving <789> Squares R1C2 and R2C1 in block 1 form a simple locked pair. These 2 squares both contain the 2 possibilities <89>. Since each of the squares must contain one of the possibilities, they can be eliminated from the other squares in the block.    R1C1 - removing <89> from <3489> leaving <34>    R1C3 - removing <89> from <34789> leaving <347>    R2C3 - removing <89> from <789> leaving <7> R2C7 can only be <3> R2C4 can only be <9> R2C1 can only be <8> R3C4 can only be <3> R7C1 can only be <4> R1C2 can only be <9> R1C1 can only be <3> R1C3 can only be <4> R8C1 can only be <9> R4C2 can only be <8> R4C3 can only be <9> R8C6 can only be <8> R8C3 can only be <3> R7C6 can only be <7> R7C9 can only be <8> R9C6 can only be <9> R3C9 can only be <7> R9C8 can only be <7> R9C3 can only be <8> R9C7 can only be <4> R1C8 can only be <8> R1C5 can only be <7> R3C8 can only be <9> R3C5 can only be <8> R4C9 can only be <4> R4C7 can only be <7> R9C9 can only be <3> [Puzzle Code = Sudoku-20191023-Hard-033607]