EXTREMEPUZZLE BOOKS

Extreme Sudoku 3, puzzle 34: step-by-step solution

Step through the whole solution, or skip to the hard parts. Blue digits are placed by the walkthrough; red strike-through marks a candidate being ruled out.

Puzzle
Sudoku, number 34 of 150 in Extreme Sudoku 3
Difficulty
Expert 7 (expert and beyond), from the opening third of the book
Key technique
Nice Loops/AICs
Hard steps
29 of 59 steps need an advanced or expert technique

Blue digits are placed by the walkthrough. Red strike-through marks a candidate being ruled out. Cells are named by row and column: R3C5 is row 3, column 5. Arrow keys step too.

The key technique: Nice Loops/AICs

An alternating chain of strong and weak links. Whichever end is true, the conclusion holds, so the digit at the marked cell is ruled out.

Other advanced and expert techniques in this solve: ALS-XZ (×7), XY-Chain (×4), WXYZ-Wing (×2), Cell Forcing Chains, Empty Rectangle, Finned Fish, Sue de Coq, W-Wing, X-Wing/Swordfish, XY-Wing, XYZ-Wing.

Every move above the basics is listed on the sudoku techniques page, each with a one-sentence explanation and worked examples from the books.

The hard steps, in text (24 of 29)
  1. Step 5 · XYZ-Wing advanced
    Rules out 9 from R2C5.
  2. Step 6 · Finned Fish expert
    Rules out 7 from R9C6.
  3. Step 8 · ALS-XZ expert
    Rules out 5 from R2C6, R4C5, R6C5.
  4. Step 12 · Empty Rectangle advanced
    Rules out 1 from R9C1.
  5. Step 13 · ALS-XZ expert
    Rules out 5 from R4C3.
  6. Step 14 · ALS-XZ expert
    Rules out 7 from R3C7.
  7. Step 15 · ALS-XZ expert
    Rules out 1 from R7C1.
  8. Step 16 · Nice Loops/AICs expert
    Rules out 1 from R7C4.
  9. Step 17 · Nice Loops/AICs expert
    Rules out 1 from R9C4.
  10. Step 18 · ALS-XZ expert
    Rules out 1 from R7C3.
  11. Step 19 · ALS-XZ expert
    Rules out 5 from R5C3.
  12. Step 20 · WXYZ-Wing expert
    Rules out 2 from R4C3.
  13. Step 21 · Nice Loops/AICs expert
    Rules out 7 from R2C6.
  14. Step 22 · Nice Loops/AICs expert
    Rules out 5 from R9C2.
  15. Step 24 · Nice Loops/AICs expert
    Rules out 2 from R7C3.
  16. Step 26 · Nice Loops/AICs expert
    Rules out 4 from R3C1.
  17. Step 30 · Nice Loops/AICs expert
    Rules out 5 from R8C8.
  18. Step 31 · Nice Loops/AICs expert
    Rules out 1 from R8C8.
  19. Step 32 · Sue de Coq expert
    Rules out 6 from R8C7.
  20. Step 33 · WXYZ-Wing expert
    Rules out 5 from R5C7.
  21. Step 34 · Cell Forcing Chains expert
    Rules out 2 from R1C2.
  22. Step 36 · ALS-XZ expert
    Rules out 2 from R7C1.
  23. Step 42 · X-Wing/Swordfish advanced
    Rules out 1 from R2C1, R9C8.
  24. Step 43 · XY-Chain expert
    Rules out 1 from R1C5, R8C4.

The book

Volume three: 150 new classic 9×9 grids, none repeated from books 1 or 2, ramping from hard to brutal.

150 new puzzles. Expert and beyond. Puzzles by M. J. Bailey. Paperback, 5 × 8 in, 196 pages, £9.99 / $11.99. Every solution in the book carries a QR code to its own walkthrough, so you can check one step without seeing the whole answer.

On Amazon from 8 Dec About the book

Try a free sample puzzle (PDF) · prints on A4 or US Letter

More step-by-step solutions: Extreme Sudoku 1 · Extreme Killer Sudoku 1 · Extreme Sudoku 2 · Extreme Killer Sudoku 2 · Extreme Killer Sudoku 3.