EXTREMEPUZZLE BOOKS

Extreme Sudoku 3, puzzle 64: 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 64 of 150 in Extreme Sudoku 3
Difficulty
Expert 6 (expert and beyond), from the middle third of the book
Key technique
WXYZ-Wing
Hard steps
15 of 37 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: WXYZ-Wing

Four cells holding four digits between them, where only one digit is not confined. That digit is removed from cells that see all its copies.

Other advanced and expert techniques in this solve: ALS-XZ (×3), Nice Loops/AICs (×3), XY-Chain (×2), Cell Forcing Chains, Finned Fish, W-Wing, X-Wing/Swordfish.

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 (15)
  1. Step 6 · WXYZ-Wing expert
    Rules out 8 from R6C7, R6C9.
  2. Step 7 · ALS-XZ expert
    Rules out 8 from R6C3.
  3. Step 8 · ALS-XZ expert
    Rules out 3 from R9C9.
  4. Step 9 · ALS-XZ expert
    Rules out 3 from R9C7.
  5. Step 10 · Nice Loops/AICs expert
    Rules out 1 from R1C8.
  6. Step 13 · WXYZ-Wing expert
    Rules out 8 from R3C9.
  7. Step 14 · Nice Loops/AICs expert
    Rules out 8 from R3C1.
  8. Step 15 · Nice Loops/AICs expert
    Rules out 8 from R7C7.
  9. Step 16 · Cell Forcing Chains expert
    Rules out 8 from R1C4.
  10. Step 18 · XY-Chain expert
    Rules out 8 from R9C9.
  11. Step 19 · WXYZ-Wing expert
    Rules out 7 from R1C1, R3C7.
  12. Step 22 · Finned Fish expert
    Rules out 7 from R7C4.
  13. Step 26 · XY-Chain expert
    Rules out 3 from R8C5.
  14. Step 30 · X-Wing/Swordfish advanced
    Rules out 8 from R2C1, R2C9, R4C9, R5C1.
  15. Step 32 · W-Wing advanced
    Rules out 5 from R4C9, R6C9, R7C7.

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.