Variations on Advanced Sudoku Logic Puzzles (Vol 1) Step-by-Step Instructions for Puzzle 161   (141/256) Diff: 19/997.9984.5212.2C89.9951 The numbers in the puzzle below refer to the step number at which the value of the location can be deduced. Locations without step numbers contain the initial values found in corresponding puzzle in your edition of the book.

Rows are numbered top to bottom, columns from left to right, and rectangles from left to right and then top to bottom. Coordinates are (col, row). Precise details on numbering within each group are specified in the on-line instructions for 'Sudoku-16' puzzles.

Step 1. There are 20 independent moves.

• The only spot left for 3 in the 6th row is at (3, 6).
• The only spot left for B in the 7th row is at (12, 7).
• The only spot left for 3 in the 16th row is at (9, 16).
• The only spot left for 3 in the 4th column is at (4, 15).
• The only spot left for B in the 4th column is at (4, 4).
• The only spot left for 3 in the 2nd 4x4 square is at (6, 3).
• The only spot left for F in the 4th 4x4 square is at (14, 1).
• The only spot left for B in the 5th 4x4 square is at (1, 6).
• The only spot left for F in the 6th 4x4 square is at (8, 8).
• The only spot left for 6 in the 6th 4x4 square is at (6, 5).
• The only spot left for A in the 7th 4x4 square is at (10, 6).
• The only spot left for A in the 8th 4x4 square is at (16, 8).
• The only spot left for F in the 9th 4x4 square is at (2, 12).
• The only spot left for 2 in the 10th 4x4 square is at (8, 11).
• The only spot left for B in the 10th 4x4 square is at (6, 11).
• The only spot left for A in the 12th 4x4 square is at (13, 10).
• The only spot left for 2 in the 14th 4x4 square is at (7, 13).
• The only spot left for F in the 15th 4x4 square is at (12, 15).
• The only spot left for 1 in the 16th 4x4 square is at (13, 14).
• The only spot left for B in the 16th 4x4 square is at (16, 13).

Step 2. There are 9 independent moves.

• The only spot left for 1 in the 6th row is at (9, 6).
• The only spot left for F in the 11th row is at (13, 11).
• The only spot left for 9 in the 15th row is at (6, 15).
• The only spot left for 8 in the 2nd column is at (2, 15).
• The only spot left for 1 in the 5th 4x4 square is at (1, 8).
• The only spot left for 4 in the 5th 4x4 square is at (3, 7).
• The only spot left for 8 in the 6th 4x4 square is at (7, 5).
• The only spot left for 6 in the 9th 4x4 square is at (4, 10).
• The only spot left for 9 in the 13th 4x4 square is at (4, 13).

Step 3. There are 7 independent moves.

• The only spot left for 3 in the 5th row is at (16, 5).
• The only spot left for 2 in the 3rd column is at (3, 1).
• The only spot left for 4 in the 7th column is at (7, 9).
• The only spot left for 3 in the 6th 4x4 square is at (7, 7).
• The only spot left for 1 in the 6th 4x4 square is at (8, 5).
• The only spot left for 6 in the 7th 4x4 square is at (12, 6).
• The only spot left for 6 in the 13th 4x4 square is at (2, 14).

Step 4. There are 9 independent moves.

• The only spot left for 8 in the 6th row is at (14, 6).
• The only spot left for E in the 2nd column is at (2, 2).
• The only spot left for A in the 3rd column is at (3, 13).
• The only spot left for F in the 7th column is at (7, 14).
• The only spot left for 2 in the 2nd 4x4 square is at (5, 2).
• The only spot left for F in the 10th 4x4 square is at (6, 9).
• The only spot left for 7 in the 10th 4x4 square is at (5, 9).
• The only spot left for 6 in the 11th 4x4 square is at (9, 12).
• The only spot left for 6 in the 16th 4x4 square is at (15, 15).

Step 5. There are 11 independent moves.

• The only spot left for 7 in the 2nd row is at (7, 2).
• The only spot left for 6 in the 4th row is at (16, 4).
• The only spot left for 4 in the 6th row is at (5, 6).
• The only spot left for 5 in the 6th row is at (2, 6).
• The only spot left for 7 in the 14th row is at (8, 14).
• The only spot left for 5 in the 14th row is at (3, 14).
• The only spot left for A in the 6th column is at (6, 4).
• The only spot left for D in the 2nd 4x4 square is at (5, 1).
• The only spot left for 2 in the 3rd 4x4 square is at (10, 3).
• The only spot left for 5 in the 14th 4x4 square is at (7, 16).
• The only spot left for A in the 14th 4x4 square is at (5, 16).

Step 6. There are 8 independent moves.

• The only spot left for 1 in the 4th row is at (7, 4).
• The only spot left for C in the 5th column is at (5, 12).
• The only spot left for 0 in the 7th column is at (7, 10).
• The only spot left for 6 in the 10th column is at (10, 13).
• The only spot left for A in the 1st 4x4 square is at (1, 1).
• The only spot left for C in the 2nd 4x4 square is at (8, 4).
• The only spot left for 0 in the 2nd 4x4 square is at (6, 2).
• The only spot left for 6 in the 3rd 4x4 square is at (11, 3).

Step 7. There are 4 independent moves.

• The only spot left for C in the 1st 4x4 square is at (4, 1).
• The only spot left for 1 in the 10th 4x4 square is at (6, 10).
• The only spot left for 0 in the 14th 4x4 square is at (8, 15).
• The only spot left for C in the 14th 4x4 square is at (6, 14).

Step 8. There are 5 independent moves.

• The only spot left for 1 in the 1st row is at (11, 1).
• The only spot left for E in the 8th column is at (8, 12).
• The only spot left for 1 in the 1st 4x4 square is at (4, 2).
• The only spot left for 8 in the 10th 4x4 square is at (6, 12).
• The only spot left for E in the 14th 4x4 square is at (6, 13).

Step 9. There are 2 independent moves.

• The only spot left for 8 in the 9th 4x4 square is at (1, 10).
• The only spot left for 1 in the 11th 4x4 square is at (10, 9).

Step 10. There is 1 independent move.

• The only spot left for 5 in the 9th row is at (4, 9).

Step 11. There are 2 independent moves.

• The only spot left for D in the 4th column is at (4, 3).
• The only spot left for 5 in the 1st 4x4 square is at (1, 3).

Step 12. There are 2 independent moves.

• The only spot left for 4 in the 4th column is at (4, 11).
• The only spot left for 4 in the 1st 4x4 square is at (1, 4).

Step 13. There are 3 independent moves.

• D must be placed at (1, 12) because it is the only value left that is not already in the 12th row, the 1st column or the 9th 4x4 square.
• E must be placed at (16, 7) because it is the only value left that is not already in the 7th row, the 16th column or the 8th 4x4 square.
• 4 must be placed at (13, 3) because it is the only value left that is not already in the 3rd row, the 13th column or the 4th 4x4 square.

Step 14. There are 8 independent moves.

• The only spot left for E in the 9th row is at (3, 9).
• The only spot left for E in the 14th row is at (10, 14).
• The only spot left for 4 in the 9th column is at (9, 15).
• The only spot left for 4 in the 16th column is at (16, 14).
• The only spot left for 4 in the 3rd 4x4 square is at (11, 2).
• The only spot left for E in the 6th 4x4 square is at (5, 5).
• The only spot left for 4 in the 8th 4x4 square is at (15, 5).
• The only spot left for D in the 13th 4x4 square is at (3, 15).

Step 15. There are 13 independent moves.

• The only spot left for 9 in the 2nd row is at (16, 2).
• The only spot left for C in the 9th row is at (11, 9).
• The only spot left for E in the 10th row is at (15, 10).
• The only spot left for D in the 14th row is at (11, 14).
• The only spot left for C in the 15th row is at (1, 15).
• The only spot left for C in the 9th column is at (9, 5).
• The only spot left for 9 in the 11th column is at (11, 8).
• The only spot left for 9 in the 3rd 4x4 square is at (9, 3).
• The only spot left for 0 in the 6th 4x4 square is at (5, 7).
• The only spot left for C in the 9th 4x4 square is at (3, 10).
• The only spot left for 4 in the 12th 4x4 square is at (14, 12).
• The only spot left for C in the 15th 4x4 square is at (10, 16).
• The only spot left for D in the 16th 4x4 square is at (14, 13).

Step 16. There are 15 independent moves.

• The only spot left for 0 in the 3rd row is at (16, 3).
• The only spot left for 7 in the 5th row is at (13, 5).
• The only spot left for E in the 15th row is at (14, 15).
• The only spot left for 7 in the 9th column is at (9, 11).
• The only spot left for 8 in the 10th column is at (10, 11).
• The only spot left for 0 in the 14th column is at (14, 16).
• The only spot left for 5 in the 14th column is at (14, 8).
• The only spot left for D in the 16th column is at (16, 9).
• The only spot left for 0 in the 3rd 4x4 square is at (9, 1).
• The only spot left for C in the 5th 4x4 square is at (2, 7).
• The only spot left for 8 in the 7th 4x4 square is at (9, 8).
• The only spot left for 7 in the 7th 4x4 square is at (11, 7).
• The only spot left for 0 in the 7th 4x4 square is at (10, 5).
• The only spot left for D in the 11th 4x4 square is at (10, 10).
• The only spot left for E in the 13th 4x4 square is at (1, 16).

Step 17. There are 16 independent moves.

• The only spot left for 8 in the 1st row is at (15, 1).
• The only spot left for D in the 2nd row is at (12, 2).
• The only spot left for D in the 5th row is at (2, 5).
• The only spot left for 2 in the 7th row is at (13, 7).
• The only spot left for E in the 9th column is at (9, 4).
• The only spot left for 5 in the 10th column is at (10, 2).
• The only spot left for 8 in the 11th column is at (11, 13).
• The only spot left for D in the 13th column is at (13, 4).
• The only spot left for 7 in the 14th column is at (14, 4).
• The only spot left for 8 in the 16th column is at (16, 16).
• The only spot left for 8 in the 3rd 4x4 square is at (12, 4).
• The only spot left for 2 in the 5th 4x4 square is at (2, 8).
• The only spot left for D in the 8th 4x4 square is at (15, 8).
• The only spot left for E in the 11th 4x4 square is at (12, 11).
• The only spot left for 8 in the 12th 4x4 square is at (13, 9).
• The only spot left for 7 in the 16th 4x4 square is at (15, 16).

Step 18. There are 5 independent moves.

• The only spot left for 5 in the 11th row is at (15, 11).
• The only spot left for 0 in the 11th column is at (11, 11).
• The only spot left for 2 in the 4th 4x4 square is at (15, 4).
• The only spot left for 5 in the 11th 4x4 square is at (12, 12).
• The only spot left for 0 in the 15th 4x4 square is at (12, 13).

Step 19. There is 1 independent move.

• The only spot left for 0 in the 12th 4x4 square is at (15, 12).