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Sudoku #17 — the solutions

The three Sudoku boards from October 17, 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 8 | · · · | · 4 ·
· 2 1 | · · 8 | 3 · 5
6 · 4 | · 7 · | · · ·
------+-------+------
3 · · | 1 5 4 | 8 · 6
· · · | 7 · 6 | · · ·
1 · 6 | 2 8 3 | · · 9
------+-------+------
· · · | · 6 · | 2 · 7
5 · 2 | 4 · · | 6 3 ·
· 6 · | · · · | 1 9 ·

The solution

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

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

The board

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

The solution

6 4 3 | 1 7 9 | 5 2 8
2 7 1 | 6 5 8 | 3 4 9
9 8 5 | 2 4 3 | 7 6 1
------+-------+------
8 3 4 | 7 1 5 | 2 9 6
7 9 6 | 4 3 2 | 1 8 5
5 1 2 | 9 8 6 | 4 7 3
------+-------+------
4 6 8 | 3 2 1 | 9 5 7
1 2 9 | 5 6 7 | 8 3 4
3 5 7 | 8 9 4 | 6 1 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. 58 steps; yours need not match, and any order that never guesses ends on the same grid.

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

Hard — 28 digits given

Beyond singles, this board asks for an X-wing and an XY-wing.

The board

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

The solution

1 7 5 | 9 4 6 | 8 2 3
3 9 4 | 7 2 8 | 5 6 1
2 6 8 | 1 5 3 | 4 9 7
------+-------+------
9 1 6 | 3 8 2 | 7 5 4
4 3 2 | 6 7 5 | 1 8 9
8 5 7 | 4 9 1 | 6 3 2
------+-------+------
5 4 9 | 2 6 7 | 3 1 8
7 8 3 | 5 1 9 | 2 4 6
6 2 1 | 8 3 4 | 9 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. 55 steps; yours need not match, and any order that never guesses ends on the same grid.

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