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Sudoku #15 — the solutions

The three Sudoku boards from October 15, 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

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

The solution

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

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

Medium — 29 digits given

Beyond singles, this board asks for a claimed box.

The board

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

The solution

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

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. 53 steps; yours need not match, and any order that never guesses ends on the same grid.

  1. Row 1, column 1 is 2. 2 has only one place left in the top-left box.
  2. Row 2, column 3 is 7. 7 has only one place left in row 2.
  3. Row 2, column 8 is 3. 3 has only one place left in row 2.
  4. Row 2, column 4 is 9. 9 has only one place left in row 2.
  5. Row 2, column 9 is 2. 2 has only one place left in row 2.
  6. Row 5, column 6 is 9. 9 has only one place left in row 5.
  7. Row 5, column 4 is 2. 2 has only one place left in the center box.
  8. Row 5, column 9 is 5. 5 has only one place left in row 5.
  9. Row 5, column 1 is 7. 7 has only one place left in row 5.
  10. Row 8, column 1 is 3. Nothing but 3 is left for this cell.
  11. Row 4, column 3 is 3. 3 has only one place left in the middle-left box.
  12. Row 8, column 2 is 4. Nothing but 4 is left for this cell.
  13. In column 8, 4 can only sit inside the bottom-right box, so it leaves the rest of that box.
  14. Row 9, column 9 is 8. Nothing but 8 is left for this cell.
  15. Row 7, column 3 is 8. 8 has only one place left in the bottom-left box.
  16. Row 9, column 3 is 5. 5 has only one place left in the bottom-left box.
  17. Row 8, column 6 is 8. 8 has only one place left in the bottom-center box.
  18. Row 8, column 7 is 5. 5 has only one place left in row 8.
  19. Row 1, column 6 is 7. Nothing but 7 is left for this cell.
  20. Row 6, column 6 is 6. Nothing but 6 is left for this cell.
  21. Row 4, column 1 is 6. 6 has only one place left in the middle-left box.
  22. Row 7, column 2 is 6. 6 has only one place left in the bottom-left box.
  23. Row 3, column 3 is 6. 6 has only one place left in the top-left box.
  24. Row 9, column 1 is 1. 1 has only one place left in the bottom-left box.
  25. Row 7, column 4 is 1. 1 has only one place left in the bottom-center box.
  26. Row 9, column 4 is 4. 4 has only one place left in the bottom-center box.
  27. Row 9, column 5 is 6. 6 has only one place left in the bottom-center box.
  28. Row 7, column 8 is 4. 4 has only one place left in the bottom-right box.
  29. Row 7, column 7 is 7. 7 has only one place left in the bottom-right box.
  30. Row 4, column 8 is 7. 7 has only one place left in the middle-right box.
  31. Row 6, column 5 is 7. 7 has only one place left in the center box.
  32. Row 9, column 7 is 2. 2 has only one place left in the bottom-right box.
  33. Row 9, column 8 is 9. 9 has only one place left in the bottom-right box.
  34. Row 4, column 7 is 1. 1 has only one place left in row 4.
  35. Row 1, column 9 is 1. 1 has only one place left in the top-right box.
  36. Row 3, column 2 is 1. 1 has only one place left in the top-left box.
  37. Row 1, column 2 is 3. 3 has only one place left in the top-left box.
  38. Row 1, column 3 is 9. 9 has only one place left in the top-left box.
  39. Row 3, column 5 is 3. 3 has only one place left in the top-center box.
  40. Row 3, column 6 is 2. 2 has only one place left in the top-center box.
  41. Row 3, column 4 is 5. 5 has only one place left in the top-center box.
  42. Row 1, column 5 is 8. 8 has only one place left in the top-center box.
  43. Row 1, column 7 is 4. 4 has only one place left in the top-right box.
  44. Row 3, column 7 is 9. 9 has only one place left in the top-right box.
  45. Row 3, column 8 is 8. 8 has only one place left in the top-right box.
  46. Row 6, column 3 is 1. 1 has only one place left in the middle-left box.
  47. Row 6, column 2 is 9. 9 has only one place left in the middle-left box.
  48. Row 4, column 5 is 5. 5 has only one place left in the center box.
  49. Row 4, column 4 is 8. 8 has only one place left in the center box.
  50. Row 6, column 9 is 4. 4 has only one place left in the middle-right box.
  51. Row 6, column 7 is 8. 8 has only one place left in the middle-right box.
  52. Row 7, column 5 is 2. 2 has only one place left in the bottom-center box.
  53. Row 7, column 6 is 5. 5 has only one place left in the bottom-center box.

Hard — 26 digits given

Beyond singles, this board asks for a pointing line (5 times), a naked pair and a hidden pair.

The board

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

The solution

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

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. 62 steps; yours need not match, and any order that never guesses ends on the same grid.

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