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Sudoku #23 — the solutions

The three Sudoku boards from October 23, 2026 — Easy, Medium and Hard — each with its solved grid and a path through it, step by step, that never needs a guess.

Easy — 36 digits given

Every cell falls to scanning: a digit with only one place left in a row, a column or a box.

The board

· · · | 9 5 3 | · 1 2
5 3 2 | 4 · 1 | · · ·
· 4 9 | · 2 · | 8 · ·
------+-------+------
· 7 · | 1 · · | · · ·
4 · · | 7 · 9 | · · 6
· · · | · · 2 | · 4 ·
------+-------+------
· · 4 | · 9 · | 1 3 ·
· · · | 5 · 8 | 6 9 4
9 8 · | 3 1 4 | · · ·

The solution

8 6 7 | 9 5 3 | 4 1 2
5 3 2 | 4 8 1 | 9 6 7
1 4 9 | 6 2 7 | 8 5 3
------+-------+------
6 7 8 | 1 4 5 | 3 2 9
4 2 1 | 7 3 9 | 5 8 6
3 9 5 | 8 6 2 | 7 4 1
------+-------+------
7 5 4 | 2 9 6 | 1 3 8
2 1 3 | 5 7 8 | 6 9 4
9 8 6 | 3 1 4 | 2 7 5

A path through it

The order a solver takes — always the cheapest move left, so a pattern is only reached for when the singles run dry. 45 steps; yours need not match, and any order that never guesses ends on the same grid.

  1. Row 3, column 1 is 1. 1 has only one place left in the top-left box.
  2. Row 2, column 5 is 8. 8 has only one place left in the top-center box.
  3. Row 3, column 6 is 7. 7 has only one place left in the top-center box.
  4. Row 3, column 4 is 6. 6 has only one place left in the top-center box.
  5. Row 3, column 9 is 3. 3 has only one place left in the top-right box.
  6. Row 1, column 7 is 4. 4 has only one place left in the top-right box.
  7. Row 3, column 8 is 5. 5 has only one place left in the top-right box.
  8. Row 2, column 8 is 6. 6 has only one place left in the top-right box.
  9. Row 6, column 2 is 9. 9 has only one place left in the middle-left box.
  10. Row 4, column 5 is 4. 4 has only one place left in the center box.
  11. Row 4, column 6 is 5. 5 has only one place left in the center box.
  12. Row 6, column 5 is 6. 6 has only one place left in the center box.
  13. Row 5, column 5 is 3. 3 has only one place left in the center box.
  14. Row 6, column 4 is 8. 8 has only one place left in the center box.
  15. Row 6, column 9 is 1. 1 has only one place left in the middle-right box.
  16. Row 6, column 7 is 7. 7 has only one place left in the middle-right box.
  17. Row 2, column 9 is 7. 7 has only one place left in the top-right box.
  18. Row 2, column 7 is 9. 9 has only one place left in the top-right box.
  19. Row 4, column 7 is 3. 3 has only one place left in the middle-right box.
  20. Row 5, column 7 is 5. 5 has only one place left in the middle-right box.
  21. Row 6, column 3 is 5. 5 has only one place left in the middle-left box.
  22. Row 6, column 1 is 3. 3 has only one place left in the middle-left box.
  23. Row 4, column 9 is 9. 9 has only one place left in the middle-right box.
  24. Row 8, column 3 is 3. 3 has only one place left in the bottom-left box.
  25. Row 8, column 2 is 1. 1 has only one place left in the bottom-left box.
  26. Row 5, column 3 is 1. 1 has only one place left in the middle-left box.
  27. Row 7, column 2 is 5. 5 has only one place left in the bottom-left box.
  28. Row 7, column 4 is 2. 2 has only one place left in the bottom-center box.
  29. Row 8, column 1 is 2. 2 has only one place left in the bottom-left box.
  30. Row 5, column 2 is 2. 2 has only one place left in the middle-left box.
  31. Row 4, column 8 is 2. 2 has only one place left in the middle-right box.
  32. Row 5, column 8 is 8. 8 has only one place left in the middle-right box.
  33. Row 7, column 6 is 6. 6 has only one place left in the bottom-center box.
  34. Row 9, column 3 is 6. 6 has only one place left in the bottom-left box.
  35. Row 4, column 1 is 6. 6 has only one place left in the middle-left box.
  36. Row 1, column 2 is 6. 6 has only one place left in the top-left box.
  37. Row 4, column 3 is 8. 8 has only one place left in the middle-left box.
  38. Row 1, column 1 is 8. 8 has only one place left in the top-left box.
  39. Row 1, column 3 is 7. 7 has only one place left in the top-left box.
  40. Row 7, column 1 is 7. 7 has only one place left in the bottom-left box.
  41. Row 8, column 5 is 7. 7 has only one place left in the bottom-center box.
  42. Row 9, column 7 is 2. 2 has only one place left in the bottom-right box.
  43. Row 9, column 9 is 5. 5 has only one place left in the bottom-right box.
  44. Row 9, column 8 is 7. 7 has only one place left in the bottom-right box.
  45. Row 7, column 9 is 8. 8 has only one place left in the bottom-right box.

Medium — 28 digits given

Beyond singles, this board asks for a pointing line, a claimed box and a naked pair.

The board

· · · | 5 · 1 | · 9 6
1 · 5 | · · · | · 2 ·
· · 3 | · 2 · | · · ·
------+-------+------
6 8 · | · · · | 9 · ·
7 · · | 6 · 9 | · · 1
· · 1 | · · · | · 6 4
------+-------+------
· · · | · 6 · | 2 · ·
· 1 · | · · · | 6 · 3
8 5 · | 2 · 3 | · · ·

The solution

4 2 8 | 5 7 1 | 3 9 6
1 6 5 | 9 3 4 | 8 2 7
9 7 3 | 8 2 6 | 1 4 5
------+-------+------
6 8 4 | 1 5 7 | 9 3 2
7 3 2 | 6 4 9 | 5 8 1
5 9 1 | 3 8 2 | 7 6 4
------+-------+------
3 4 9 | 7 6 5 | 2 1 8
2 1 7 | 4 9 8 | 6 5 3
8 5 6 | 2 1 3 | 4 7 9

A path through it

The order a solver takes — always the cheapest move left, so a pattern is only reached for when the singles run dry. 56 steps; yours need not match, and any order that never guesses ends on the same grid.

  1. Row 1, column 3 is 8. 8 has only one place left in the top-left box.
  2. Row 6, column 1 is 5. 5 has only one place left in the middle-left box.
  3. Row 6, column 2 is 9. 9 has only one place left in the middle-left box.
  4. Row 3, column 1 is 9. 9 has only one place left in the top-left box.
  5. Row 5, column 2 is 3. 3 has only one place left in the middle-left box.
  6. Row 4, column 9 is 2. 2 has only one place left in the middle-right box.
  7. Row 5, column 3 is 2. 2 has only one place left in the middle-left box.
  8. Row 4, column 3 is 4. 4 has only one place left in the middle-left box.
  9. Row 6, column 6 is 2. 2 has only one place left in the center box.
  10. Row 5, column 5 is 4. 4 has only one place left in the center box.
  11. Row 8, column 1 is 2. 2 has only one place left in the bottom-left box.
  12. Row 1, column 2 is 2. 2 has only one place left in the top-left box.
  13. Row 7, column 1 is 3. 3 has only one place left in the bottom-left box.
  14. Row 7, column 2 is 4. 4 has only one place left in the bottom-left box.
  15. Row 1, column 1 is 4. 4 has only one place left in the top-left box.
  16. Row 9, column 3 is 6. 6 has only one place left in the bottom-left box.
  17. Row 4, column 8 is 3. 3 has only one place left in column 8.
  18. Row 6, column 7 is 7. 7 has only one place left in the middle-right box.
  19. Row 1, column 5 is 7. 7 has only one place left in row 1.
  20. Row 1, column 7 is 3. 3 has only one place left in row 1.
  21. In the bottom-center box, 4 can only sit in row 8, so it leaves the rest of that row.
  22. In row 9, 7 can only sit inside the bottom-right box, so it leaves the rest of that box.
  23. Two cells in column 8 hold only 5 and 8, so no other cell there can.
  24. Row 7, column 8 is 1. Nothing but 1 is left for this cell.
  25. Row 3, column 7 is 1. 1 has only one place left in the top-right box.
  26. Row 3, column 9 is 5. 5 has only one place left in the top-right box.
  27. Row 9, column 5 is 1. 1 has only one place left in the bottom-center box.
  28. Row 4, column 4 is 1. 1 has only one place left in the center box.
  29. Row 4, column 6 is 7. 7 has only one place left in the center box.
  30. Row 4, column 5 is 5. 5 has only one place left in the center box.
  31. Row 8, column 8 is 5. 5 has only one place left in the bottom-right box.
  32. Row 5, column 7 is 5. 5 has only one place left in the middle-right box.
  33. Row 5, column 8 is 8. 8 has only one place left in the middle-right box.
  34. Row 7, column 6 is 5. 5 has only one place left in the bottom-center box.
  35. Row 7, column 9 is 8. 8 has only one place left in the bottom-right box.
  36. Row 2, column 7 is 8. 8 has only one place left in the top-right box.
  37. Row 3, column 8 is 4. 4 has only one place left in the top-right box.
  38. Row 2, column 9 is 7. 7 has only one place left in the top-right box.
  39. Row 3, column 2 is 7. 7 has only one place left in the top-left box.
  40. Row 2, column 2 is 6. 6 has only one place left in the top-left box.
  41. Row 3, column 6 is 6. 6 has only one place left in the top-center box.
  42. Row 3, column 4 is 8. 8 has only one place left in the top-center box.
  43. Row 6, column 5 is 8. 8 has only one place left in the center box.
  44. Row 6, column 4 is 3. 3 has only one place left in the center box.
  45. Row 2, column 5 is 3. 3 has only one place left in the top-center box.
  46. Row 2, column 4 is 9. 9 has only one place left in the top-center box.
  47. Row 2, column 6 is 4. 4 has only one place left in the top-center box.
  48. Row 8, column 4 is 4. 4 has only one place left in the bottom-center box.
  49. Row 7, column 4 is 7. 7 has only one place left in the bottom-center box.
  50. Row 8, column 3 is 7. 7 has only one place left in the bottom-left box.
  51. Row 7, column 3 is 9. 9 has only one place left in the bottom-left box.
  52. Row 8, column 6 is 8. 8 has only one place left in the bottom-center box.
  53. Row 8, column 5 is 9. 9 has only one place left in the bottom-center box.
  54. Row 9, column 7 is 4. 4 has only one place left in the bottom-right box.
  55. Row 9, column 8 is 7. 7 has only one place left in the bottom-right box.
  56. Row 9, column 9 is 9. 9 has only one place left in the bottom-right box.

Hard — 28 digits given

Beyond singles, this board asks for a pointing line (3 times) and an XY-wing.

The board

· 6 4 | · 5 · | · · ·
· · · | 6 4 7 | 8 · ·
· 2 · | · · 8 | · · ·
------+-------+------
· 8 · | 9 · · | · 4 7
1 · · | · · · | · · 5
2 4 · | · · 3 | · 8 ·
------+-------+------
· · · | 3 · · | · 1 ·
· · 3 | 4 9 6 | · · ·
· · · | · 8 · | 4 3 ·

The solution

8 6 4 | 2 5 9 | 1 7 3
5 3 1 | 6 4 7 | 8 9 2
9 2 7 | 1 3 8 | 5 6 4
------+-------+------
3 8 5 | 9 1 2 | 6 4 7
1 7 9 | 8 6 4 | 3 2 5
2 4 6 | 5 7 3 | 9 8 1
------+-------+------
4 9 8 | 3 2 5 | 7 1 6
7 1 3 | 4 9 6 | 2 5 8
6 5 2 | 7 8 1 | 4 3 9

A path through it

The order a solver takes — always the cheapest move left, so a pattern is only reached for when the singles run dry. 57 steps; yours need not match, and any order that never guesses ends on the same grid.

  1. Row 1, column 1 is 8. 8 has only one place left in the top-left box.
  2. Row 3, column 5 is 3. 3 has only one place left in the top-center box.
  3. Row 1, column 6 is 9. 9 has only one place left in the top-center box.
  4. Row 1, column 4 is 2. 2 has only one place left in the top-center box.
  5. Row 3, column 4 is 1. 1 has only one place left in the top-center box.
  6. Row 3, column 9 is 4. 4 has only one place left in the top-right box.
  7. Row 5, column 6 is 4. 4 has only one place left in the center box.
  8. Row 5, column 4 is 8. 8 has only one place left in the center box.
  9. Row 7, column 1 is 4. 4 has only one place left in the bottom-left box.
  10. Row 7, column 3 is 8. 8 has only one place left in the bottom-left box.
  11. Row 9, column 3 is 2. 2 has only one place left in the bottom-left box.
  12. Row 9, column 1 is 6. 6 has only one place left in the bottom-left box.
  13. Row 9, column 6 is 1. 1 has only one place left in the bottom-center box.
  14. Row 8, column 2 is 1. 1 has only one place left in the bottom-left box.
  15. Row 2, column 3 is 1. 1 has only one place left in the top-left box.
  16. Row 8, column 9 is 8. 8 has only one place left in the bottom-right box.
  17. Row 1, column 8 is 7. Nothing but 7 is left for this cell.
  18. Row 9, column 9 is 9. Nothing but 9 is left for this cell.
  19. Row 7, column 2 is 9. 9 has only one place left in the bottom-left box.
  20. In the top-left box, 3 can only sit in row 2, so it leaves the rest of that row.
  21. Row 1, column 9 is 3. 3 has only one place left in column 9.
  22. Row 1, column 7 is 1. 1 has only one place left in the top-right box.
  23. Row 6, column 9 is 1. 1 has only one place left in the middle-right box.
  24. Row 4, column 5 is 1. 1 has only one place left in the center box.
  25. Row 7, column 9 is 6. 6 has only one place left in column 9.
  26. Row 2, column 9 is 2. 2 has only one place left in column 9.
  27. In the middle-left box, 9 can only sit in column 3, so it leaves the rest of that column.
  28. In the bottom-center box, 2 can only sit in row 7, so it leaves the rest of that row.
  29. XY-wing: one of its two wings must be 7, so no cell that sees both can be.
  30. Row 5, column 2 is 7. 7 has only one place left in the middle-left box.
  31. Row 4, column 1 is 3. 3 has only one place left in the middle-left box.
  32. Row 2, column 2 is 3. 3 has only one place left in the top-left box.
  33. Row 5, column 7 is 3. 3 has only one place left in the middle-right box.
  34. Row 8, column 1 is 7. 7 has only one place left in the bottom-left box.
  35. Row 3, column 3 is 7. 7 has only one place left in the top-left box.
  36. Row 9, column 2 is 5. 5 has only one place left in the bottom-left box.
  37. Row 7, column 6 is 5. 5 has only one place left in the bottom-center box.
  38. Row 6, column 4 is 5. 5 has only one place left in the center box.
  39. Row 4, column 3 is 5. 5 has only one place left in the middle-left box.
  40. Row 6, column 5 is 7. 7 has only one place left in the center box.
  41. Row 5, column 5 is 6. 6 has only one place left in the center box.
  42. Row 6, column 3 is 6. 6 has only one place left in the middle-left box.
  43. Row 5, column 3 is 9. 9 has only one place left in the middle-left box.
  44. Row 4, column 6 is 2. 2 has only one place left in the center box.
  45. Row 5, column 8 is 2. 2 has only one place left in the middle-right box.
  46. Row 4, column 7 is 6. 6 has only one place left in the middle-right box.
  47. Row 3, column 8 is 6. 6 has only one place left in the top-right box.
  48. Row 6, column 7 is 9. 9 has only one place left in the middle-right box.
  49. Row 2, column 8 is 9. 9 has only one place left in the top-right box.
  50. Row 3, column 1 is 9. 9 has only one place left in the top-left box.
  51. Row 2, column 1 is 5. 5 has only one place left in the top-left box.
  52. Row 3, column 7 is 5. 5 has only one place left in the top-right box.
  53. Row 7, column 5 is 2. 2 has only one place left in the bottom-center box.
  54. Row 9, column 4 is 7. 7 has only one place left in the bottom-center box.
  55. Row 8, column 7 is 2. 2 has only one place left in the bottom-right box.
  56. Row 8, column 8 is 5. 5 has only one place left in the bottom-right box.
  57. Row 7, column 7 is 7. 7 has only one place left in the bottom-right box.

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About Sudoku

Sudoku on Noggin is three boards a day, on the second shelf: every entry is checked at once, a hint fills the next cell a solver would and says why, and the first board finished is the day’s score, outside the daily line-up. How to play Sudoku, or play today’s.