EXTREMEPUZZLE BOOKS

Extreme Sudoku 1, puzzle 38: 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 38 of 150 in Extreme Sudoku 1
Difficulty
Expert 6 (expert and beyond), from the opening third of the book
Key technique
XY-Chain
Hard steps
22 of 47 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 (×4), WXYZ-Wing (×3), Nice Loops/AICs (×2), X-Wing/Swordfish (×2), 2-String Kite, Empty Rectangle, Finned Fish, Sue de Coq, W-Wing, XY-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 (22)
  1. Step 5 · Finned Fish expert
    Rules out 9 from R4C4.
  2. Step 6 · WXYZ-Wing expert
    Rules out 4 from R9C5.
  3. Step 7 · WXYZ-Wing expert
    Rules out 7 from R8C4, R9C9.
  4. Step 10 · WXYZ-Wing expert
    Rules out 8 from R4C5.
  5. Step 11 · Empty Rectangle advanced
    Rules out 8 from R1C8.
  6. Step 12 · ALS-XZ expert
    Rules out 8 from R5C8.
  7. Step 13 · ALS-XZ expert
    Rules out 8 from R5C7.
  8. Step 14 · ALS-XZ expert
    Rules out 9 from R5C2.
  9. Step 16 · Nice Loops/AICs expert
    Rules out 9 from R4C8.
  10. Step 19 · Sue de Coq expert
    Rules out 1 from R7C9; 4 from R7C9, R8C9.
  11. Step 20 · ALS-XZ expert
    Rules out 8 from R2C9.
  12. Step 21 · Nice Loops/AICs expert
    Rules out 7 from R4C8.
  13. Step 26 · 2-String Kite advanced
    Rules out 4 from R2C4.
  14. Step 27 · W-Wing advanced
    Rules out 8 from R2C3.
  15. Step 28 · XY-Chain expert
    Rules out 2 from R4C1.
  16. Step 30 · XY-Chain expert
    Rules out 4 from R1C5.
  17. Step 33 · X-Wing/Swordfish advanced
    Rules out 4 from R8C4.
  18. Step 34 · XY-Chain expert
    Rules out 3 from R2C6.
  19. Step 35 · XY-Chain expert
    Rules out 8 from R2C2, R3C2, R6C3.
  20. Step 38 · XY-Chain expert
    Rules out 1 from R2C6, R6C4.
  21. Step 40 · X-Wing/Swordfish advanced
    Rules out 9 from R2C2, R2C4.
  22. Step 42 · XY-Wing advanced
    Rules out 2 from R8C2.

The book

Classic 9×9 sudoku with the warm-up taken out. Every grid sits at the top of the expert range or beyond it, and the book ramps from hard to brutal.

150 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.

Buy on Amazon US Buy on Amazon UK
Other Amazon stores
About the book

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

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