EXTREMEPUZZLE BOOKS

Extreme Sudoku 3, puzzle 1: 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 1 of 150 in Extreme Sudoku 3
Difficulty
Expert 5 (expert and beyond), from the opening third of the book
Key technique
XY-Chain
Hard steps
24 of 46 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: XY-Chain

A chain of two-candidate cells, each linked to the next. Whichever way the start cell goes, one end of the chain holds the digit, so cells seeing both ends cannot.

Other advanced and expert techniques in this solve: ALS-XZ (×3), Finned Fish (×3), Nice Loops/AICs (×3), XY-Wing (×3), 2-String Kite (×2), WXYZ-Wing (×2), Skyscraper, W-Wing, X-Wing/Swordfish, 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)
  1. Step 4 · Skyscraper advanced
    Rules out 1 from R2C9.
  2. Step 7 · 2-String Kite advanced
    Rules out 4 from R3C3.
  3. Step 8 · XYZ-Wing advanced
    Rules out 3 from R5C4.
  4. Step 9 · WXYZ-Wing expert
    Rules out 3 from R6C5.
  5. Step 10 · ALS-XZ expert
    Rules out 6 from R1C2.
  6. Step 11 · ALS-XZ expert
    Rules out 3 from R4C7.
  7. Step 12 · Nice Loops/AICs expert
    Rules out 6 from R1C8.
  8. Step 13 · Finned Fish expert
    Rules out 6 from R2C2.
  9. Step 14 · Nice Loops/AICs expert
    Rules out 6 from R5C5.
  10. Step 15 · Nice Loops/AICs expert
    Rules out 1 from R1C1.
  11. Step 19 · 2-String Kite advanced
    Rules out 6 from R2C7.
  12. Step 20 · Finned Fish expert
    Rules out 6 from R7C3.
  13. Step 22 · WXYZ-Wing expert
    Rules out 7 from R1C2.
  14. Step 23 · W-Wing advanced
    Rules out 4 from R1C3, R7C2.
  15. Step 25 · Finned Fish expert
    Rules out 3 from R6C7.
  16. Step 27 · ALS-XZ expert
    Rules out 7 from R4C5, R5C3.
  17. Step 28 · XY-Chain expert
    Rules out 7 from R8C2.
  18. Step 30 · XY-Wing advanced
    Rules out 8 from R6C2, R7C3.
  19. Step 33 · XY-Wing advanced
    Rules out 9 from R6C7.
  20. Step 34 · XY-Chain expert
    Rules out 3 from R1C3.
  21. Step 35 · XY-Chain expert
    Rules out 2 from R2C2, R3C7.
  22. Step 37 · XY-Chain expert
    Rules out 9 from R3C7.
  23. Step 42 · X-Wing/Swordfish advanced
    Rules out 6 from R3C9.
  24. Step 43 · XY-Wing advanced
    Rules out 3 from R7C9.

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.