EXTREMEPUZZLE BOOKS

Extreme Sudoku 3, puzzle 26: 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 26 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
19 of 44 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 (×4), Finned Fish (×2), XY-Chain (×2), XY-Wing (×2), 2-String Kite, Cell Forcing Chains, Sue de Coq, WXYZ-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 (19)
  1. Step 5 · X-Wing/Swordfish advanced
    Rules out 8 from R6C4, R6C7, R9C7, R9C8.
  2. Step 6 · Finned Fish expert
    Rules out 4 from R3C8, R3C9.
  3. Step 7 · Finned Fish expert
    Rules out 9 from R1C7.
  4. Step 8 · Nice Loops/AICs expert
    Rules out 1 from R2C4.
  5. Step 9 · Sue de Coq expert
    Rules out 1 from R9C6.
  6. Step 14 · 2-String Kite advanced
    Rules out 1 from R5C7.
  7. Step 15 · XY-Wing advanced
    Rules out 3 from R9C2.
  8. Step 16 · ALS-XZ expert
    Rules out 4 from R5C7, R5C8.
  9. Step 17 · ALS-XZ expert
    Rules out 2 from R9C9.
  10. Step 18 · Nice Loops/AICs expert
    Rules out 3 from R3C6.
  11. Step 20 · ALS-XZ expert
    Rules out 1 from R6C4.
  12. Step 21 · Nice Loops/AICs expert
    Rules out 3 from R6C9.
  13. Step 22 · ALS-XZ expert
    Rules out 1 from R5C3.
  14. Step 23 · Cell Forcing Chains expert
    Rules out 4 from R1C4.
  15. Step 27 · WXYZ-Wing expert
    Rules out 4 from R6C3.
  16. Step 29 · XY-Chain expert
    Rules out 5 from R4C1, R5C1.
  17. Step 32 · XY-Chain expert
    Rules out 3 from R8C9.
  18. Step 33 · Nice Loops/AICs expert
    Rules out 4 from R6C7.
  19. Step 41 · XY-Wing advanced
    Rules out 1 from R2C7, R4C8.

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.