Variations on Advanced Sudoku Logic Puzzles (Vol 1) Step-by-Step Instructions for Puzzle 20   (98/144) Diff: 41/3.1121.2211.111B.1A23.221C.2345.531A.2245.3333.2454 Printable puzzle or puzzle with instructions 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-12' puzzles.

Step 1. There are 3 independent moves.

• The only spot left for 1 in the 1st 4x3 rectangle is at (4, 3).
• The only spot left for A in the 5th 4x3 rectangle is at (6, 4).
• The only spot left for 6 in the 10th 4x3 rectangle is at (3, 11).

Step 2. There is 1 independent move.

• The only spot left for 6 in the 4th 4x3 rectangle is at (1, 4).

Step 3. There is 1 independent move.

• The only spot left for 0 in the 4th 4x3 rectangle is at (2, 4).

Step 4. There are 2 independent moves.

• The only spot left for 3 in the 4th row is at (5, 4).
• The only spot left for 1 in the 4th 4x3 rectangle is at (2, 6).

Step 5. There is 1 independent move.

• The only spot left for 1 in the 10th column is at (10, 5).

Step 6. There are 2 independent moves.

• The only spot left for 1 in the 5th 4x3 rectangle is at (7, 4).
• The only spot left for 7 in the 6th 4x3 rectangle is at (11, 5).

Step 7. There are 2 independent moves.

• The only spot left for 6 in the 6th 4x3 rectangle is at (12, 5).
• The only spot left for 1 in the 8th 4x3 rectangle is at (5, 8).

Step 8. There is 1 independent move.

• The only spot left for 9 in the 8th row is at (4, 8).

Step 9. There is 1 independent move.

• The only spot left for 6 in the 8th row is at (9, 8).

Step 10. There is 1 independent move.

• The only spot left for B in the 8th row is at (12, 8).

Step 11. There is 1 independent move.

• The only spot left for 5 in the 9th 4x3 rectangle is at (9, 9).

Step 12. There is 1 independent move.

• The only spot left for 5 in the 6th 4x3 rectangle is at (11, 6).

Step 13. There are 2 independent moves.

• 8 must be placed at (10, 8) because it is the only value left that is not already in the 8th row, the 10th column or the 9th 4x3 rectangle.
• 2 must be placed at (12, 4) because it is the only value left that is not already in the 4th row, the 12th column or the 6th 4x3 rectangle.

Step 14. There is 1 independent move.

• The only spot left for 2 in the 9th 4x3 rectangle is at (11, 7).

Step 15. There is 1 independent move.

• 2 must be placed at (7, 8) because it is the only value left that is not already in the 8th row, the 7th column or the 8th 4x3 rectangle.

Step 16. There are 2 independent moves.

• The only spot left for 2 in the 1st column is at (1, 6).
• The only spot left for 2 in the 7th 4x3 rectangle is at (3, 9).

Step 17. There are 3 independent moves.

• The only spot left for 4 in the 9th row is at (2, 9).
• The only spot left for 3 in the 4th 4x3 rectangle is at (4, 6).
• The only spot left for 0 in the 7th 4x3 rectangle is at (1, 7).

Step 18. There are 2 independent moves.

• The only spot left for A in the 9th row is at (4, 9).
• The only spot left for 8 in the 4th 4x3 rectangle is at (3, 5).

Step 19. There are 2 independent moves.

• The only spot left for A in the 1st 4x3 rectangle is at (2, 1).
• The only spot left for 6 in the 7th 4x3 rectangle is at (4, 7).

Step 20. There is 1 independent move.

• The only spot left for 8 in the 7th 4x3 rectangle is at (2, 7).

Step 21. There are 3 independent moves.

• 3 must be placed at (2, 12) because it is the only value left that is not already in the 12th row, the 2nd column or the 10th 4x3 rectangle.
• 4 must be placed at (7, 5) because it is the only value left that is not already in the 5th row, the 7th column or the 5th 4x3 rectangle.
• 7 must be placed at (4, 1) because it is the only value left that is not already in the 1st row, the 4th column or the 1st 4x3 rectangle.

Step 22. There are 2 independent moves.

• The only spot left for 7 in the 2nd 4x3 rectangle is at (7, 2).
• The only spot left for 7 in the 10th 4x3 rectangle is at (1, 12).

Step 23. There are 3 independent moves.

• The only spot left for 7 in the 9th row is at (8, 9).
• The only spot left for 5 in the 7th column is at (7, 10).
• The only spot left for 5 in the 2nd 4x3 rectangle is at (5, 3).

Step 24. There are 4 independent moves.

• The only spot left for 5 in the 11th row is at (12, 11).
• The only spot left for 9 in the 5th column is at (5, 7).
• The only spot left for 8 in the 7th column is at (7, 9).
• The only spot left for 5 in the 10th 4x3 rectangle is at (4, 12).

Step 25. There are 5 independent moves.

• The only spot left for 8 in the 4th column is at (4, 2).
• The only spot left for 0 in the 7th column is at (7, 1).
• The only spot left for 0 in the 8th 4x3 rectangle is at (6, 9).
• The only spot left for B in the 8th 4x3 rectangle is at (8, 7).
• The only spot left for 8 in the 10th 4x3 rectangle is at (1, 10).

Step 26. There are 5 independent moves.

• The only spot left for 0 in the 12th row is at (9, 12).
• The only spot left for B in the 5th 4x3 rectangle is at (5, 6).
• The only spot left for 6 in the 8th 4x3 rectangle is at (5, 9).
• The only spot left for 4 in the 10th 4x3 rectangle is at (3, 10).
• The only spot left for 0 in the 11th 4x3 rectangle is at (8, 11).

Step 27. There are 3 independent moves.

• The only spot left for 0 in the 3rd row is at (3, 3).
• The only spot left for 0 in the 3rd 4x3 rectangle is at (10, 2).
• The only spot left for 8 in the 5th 4x3 rectangle is at (8, 6).

Step 28. There is 1 independent move.

• The only spot left for 8 in the 2nd 4x3 rectangle is at (6, 3).

Step 29. There is 1 independent move.

• 3 must be placed at (8, 10) because it is the only value left that is not already in the 10th row, the 8th column or the 11th 4x3 rectangle.

Step 30. There are 2 independent moves.

• The only spot left for 3 in the 12th column is at (12, 2).
• The only spot left for 3 in the 12th 4x3 rectangle is at (11, 11).

Step 31. There are 2 independent moves.

• The only spot left for 3 in the 3rd row is at (1, 3).
• The only spot left for 3 in the 2nd 4x3 rectangle is at (6, 1).

Step 32. There are 4 independent moves.

• The only spot left for 6 in the 1st row is at (11, 1).
• The only spot left for 4 in the 1st 4x3 rectangle is at (1, 2).
• The only spot left for 6 in the 2nd 4x3 rectangle is at (6, 2).
• The only spot left for 3 in the 7th 4x3 rectangle is at (3, 8).

Step 33. There are 5 independent moves.

• The only spot left for B in the 1st row is at (3, 1).
• The only spot left for 9 in the 6th column is at (6, 5).
• The only spot left for 5 in the 1st 4x3 rectangle is at (3, 2).
• The only spot left for 9 in the 2nd 4x3 rectangle is at (8, 3).
• The only spot left for 5 in the 7th 4x3 rectangle is at (1, 8).

Step 34. There are 3 independent moves.

• The only spot left for 2 in the 6th column is at (6, 12).
• The only spot left for 4 in the 8th column is at (8, 1).
• The only spot left for 2 in the 5th 4x3 rectangle is at (8, 5).

Step 35. There are 3 independent moves.

• The only spot left for 1 in the 12th row is at (12, 12).
• The only spot left for 2 in the 2nd 4x3 rectangle is at (5, 1).
• The only spot left for 1 in the 11th 4x3 rectangle is at (6, 10).

Step 36. There are 3 independent moves.

• The only spot left for B in the 10th row is at (2, 10).
• The only spot left for 4 in the 12th column is at (12, 7).
• The only spot left for B in the 11th 4x3 rectangle is at (6, 11).

Step 37. There are 3 independent moves.

• The only spot left for 9 in the 10th row is at (11, 10).
• The only spot left for A in the 12th column is at (12, 10).
• The only spot left for 9 in the 10th 4x3 rectangle is at (2, 11).

Step 38. There are 2 independent moves.

• The only spot left for A in the 11th column is at (11, 3).
• The only spot left for 9 in the 3rd 4x3 rectangle is at (9, 2).

Step 39. There are 4 independent moves.

• The only spot left for B in the 9th column is at (9, 4).
• The only spot left for 4 in the 11th column is at (11, 12).
• The only spot left for 4 in the 3rd 4x3 rectangle is at (9, 3).
• The only spot left for B in the 3rd 4x3 rectangle is at (11, 2).

Step 40. There are 5 independent moves.

• The only spot left for 8 in the 12th row is at (5, 12).
• The only spot left for 4 in the 6th 4x3 rectangle is at (10, 6).
• The only spot left for 8 in the 6th 4x3 rectangle is at (11, 4).
• The only spot left for 4 in the 11th 4x3 rectangle is at (5, 11).
• The only spot left for 8 in the 12th 4x3 rectangle is at (9, 11).

Step 41. There are 4 independent moves.

• The only spot left for 7 in the 9th column is at (9, 7).
• The only spot left for A in the 10th column is at (10, 7).
• The only spot left for A in the 6th 4x3 rectangle is at (9, 6).
• The only spot left for 7 in the 12th 4x3 rectangle is at (10, 11).