Step-by-Step Solution
for Friday 23rd September Diabolical


Before

Step

After


Sudoku puzzle
First step:
Add in all possible valid pencilmarks.
Sudoku puzzle

Sudoku puzzle

Number 3 is the only value possible in cell (5,5).

Single Candidate

Sudoku puzzle

Sudoku puzzle

Number 8 is the only value possible in cell (3,5).

Single Candidate

Sudoku puzzle

Sudoku puzzle

Number 5 is the only value possible in cell (7,5).

Single Candidate

Sudoku puzzle

Sudoku puzzle

Number 9 is the only value possible in cell (7,4).

Single Candidate

Sudoku puzzle

Sudoku puzzle

Number 7 is the only value possible in cell (7,6).

Single Candidate

Sudoku puzzle

Sudoku puzzle

Number 6 is the only value possible in cell (7,8).

Single Candidate

Sudoku puzzle

Sudoku puzzle

Number 8 is the only value possible in cell (7,1).

Single Candidate

Sudoku puzzle

Sudoku puzzle

For row 6, number 8 is only possible in cell (4,6)

Single Position

Sudoku puzzle

Sudoku puzzle

For row 6, number 9 is only possible in cell (5,6)

Single Position

Sudoku puzzle

Sudoku puzzle

For row 1, number 7 is only possible in cell (8,1)

Single Position

Sudoku puzzle

Sudoku puzzle

For row 3, number 4 is only possible in cell (2,3)

Single Position

Sudoku puzzle

Sudoku puzzle

For row 6, number 4 is only possible in cell (3,6)

Single Position

Sudoku puzzle

Sudoku puzzle

Naked Pair for 5 and 9, can remove these as candidates from other cells.

Naked Pairs

Sudoku puzzle

Sudoku puzzle

For column 6, Number 9 is only possible in cell (6,2)

Single Position

Sudoku puzzle

Sudoku puzzle

For row 3, number 9 is only possible in cell (1,3)

Single Position

Sudoku puzzle

Sudoku puzzle

For column 6, Number 3 is only possible in cell (6,1)

Single Position

Sudoku puzzle

Sudoku puzzle

For column 6, Number 1 is only possible in cell (6,8)

Single Position

Sudoku puzzle

Sudoku puzzle

Number 3 is the only value possible in cell (1,8).

Single Candidate

Sudoku puzzle

Sudoku puzzle

Number 7 is the only value possible in cell (2,8).

Single Candidate

Sudoku puzzle

Sudoku puzzle

Number 4 is the only value possible in cell (9,8).

Single Candidate

Sudoku puzzle

Sudoku puzzle

For row 7, number 7 is only possible in cell (9,7)

Single Position

Sudoku puzzle

Sudoku puzzle

For box 1, candidates for 3 are all in row 2, so you can remove candidates from other blocks.

Candidate Lines

Sudoku puzzle

Sudoku puzzle

Either candidate for cell (4,8) forces 2 into cell (4,2).

Sudoku puzzle

Sudoku puzzle

For box 2, candidates for 5 are all in row 3, so you can remove candidates from other blocks.

Candidate Lines

Sudoku puzzle

Sudoku puzzle

Swordfish in columns for 6.

Swordfish

Sudoku puzzle

Sudoku puzzle

Naked Pair for 2 and 5, can remove these as candidates from other cells.

Naked Pairs

Sudoku puzzle

Sudoku puzzle

For box 7, candidates for 5 are all in row 7, so you can remove candidates from other blocks.

Candidate Lines

Sudoku puzzle

Sudoku puzzle

Either candidate for cell (9,2) forces 5 into cell (1,7).

Sudoku puzzle

Sudoku puzzle

For column 1, Number 8 is only possible in cell (1,2)

Single Position

Sudoku puzzle

Sudoku puzzle

For row 4, number 5 is only possible in cell (2,4)

Single Position

Sudoku puzzle

Sudoku puzzle

Either candidate for cell (1,1) forces 3 into cell (3,4).

Sudoku puzzle

Sudoku puzzle

For row 2, number 3 is only possible in cell (2,2)

Single Position

Sudoku puzzle

Sudoku puzzle

Either candidate for cell (9,2) forces 3 into cell (9,3).

Sudoku puzzle

Sudoku puzzle

For row 6, number 3 is only possible in cell (8,6)

Single Position

Sudoku puzzle

Sudoku puzzle

Either candidate for cell (9,2) forces 6 into cell (8,3).

Sudoku puzzle

Sudoku puzzle

Number 5 is the only value possible in cell (4,3).

Single Candidate

Sudoku puzzle

Sudoku puzzle

Number 1 is the only value possible in cell (5,3).

Single Candidate

Sudoku puzzle

Sudoku puzzle

Number 6 is the only value possible in cell (5,1).

Single Candidate

Sudoku puzzle

Sudoku puzzle

Number 4 is the only value possible in cell (5,4).

Single Candidate

Sudoku puzzle

Sudoku puzzle

Number 6 is the only value possible in cell (6,4).

Single Candidate

Sudoku puzzle

Sudoku puzzle

Number 2 is the only value possible in cell (5,7).

Single Candidate

Sudoku puzzle

Sudoku puzzle

Number 4 is the only value possible in cell (6,7).

Single Candidate

Sudoku puzzle

Sudoku puzzle

Number 8 is the only value possible in cell (8,7).

Single Candidate

Sudoku puzzle

Sudoku puzzle

Number 6 is the only value possible in cell (2,7).

Single Candidate

Sudoku puzzle

Sudoku puzzle

Number 9 is the only value possible in cell (4,8).

Single Candidate

Sudoku puzzle

Sudoku puzzle

Number 5 is the only value possible in cell (8,8).

Single Candidate

Sudoku puzzle

Sudoku puzzle

Number 1 is the only value possible in cell (8,2).

Single Candidate

Sudoku puzzle

Sudoku puzzle

Number 6 is the only value possible in cell (3,2).

Single Candidate

Sudoku puzzle

Sudoku puzzle

Number 5 is the only value possible in cell (9,2).

Single Candidate

Sudoku puzzle

Sudoku puzzle

Number 2 is the only value possible in cell (8,4).

Single Candidate

Sudoku puzzle

Sudoku puzzle

Number 1 is the only value possible in cell (1,4).

Single Candidate

Sudoku puzzle

Sudoku puzzle

Number 2 is the only value possible in cell (1,1).

Single Candidate

Sudoku puzzle

Sudoku puzzle

Number 1 is the only value possible in cell (2,1).

Single Candidate

Sudoku puzzle

Sudoku puzzle

Number 2 is the only value possible in cell (2,6).

Single Candidate

Sudoku puzzle

Sudoku puzzle

Number 1 is the only value possible in cell (9,6).

Single Candidate

Sudoku puzzle

Sudoku puzzle

Number 8 is the only value possible in cell (2,9).

Single Candidate

Sudoku puzzle

Sudoku puzzle

Number 1 is the only value possible in cell (3,9).

Single Candidate

Sudoku puzzle

Sudoku puzzle

Number 6 is the only value possible in cell (4,9).

Single Candidate

Sudoku puzzle

Sudoku puzzle

Number 5 is the only value possible in cell (5,9).

Single Candidate

Sudoku puzzle

Sudoku puzzle

Number 9 is the only value possible in cell (8,9).

Single Candidate

Sudoku puzzle

Sudoku puzzle

Number 2 is the only value possible in cell (9,9).

Single Candidate

Sudoku puzzle


For guided hints and great solving assistance like automatic pencilmarks, try Astraware Sudoku Of The Day on your phone or tablet!