EXTREMEPUZZLE BOOKS

Extreme Sudoku 2, puzzle 32: 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 32 of 150 in Extreme Sudoku 2
Difficulty
Expert 7 (expert and beyond), from the opening third of the book
Key technique
Nice Loops/AICs
Hard steps
22 of 42 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), BUG+1, Cell Forcing Chains, Empty Rectangle, Finned Fish, Jellyfish, W-Wing, WXYZ-Wing, XY-Chain.

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 7 · ALS-XZ expert
    Rules out 1 from R2C8.
  2. Step 8 · ALS-XZ expert
    Rules out 9 from R2C4.
  3. Step 9 · ALS-XZ expert
    Rules out 1 from R2C4.
  4. Step 10 · Nice Loops/AICs expert
    Rules out 9 from R4C8.
  5. Step 11 · Nice Loops/AICs expert
    Rules out 2 from R1C1.
  6. Step 13 · Nice Loops/AICs expert
    Rules out 9 from R8C5.
  7. Step 14 · Nice Loops/AICs expert
    Rules out 9 from R7C7.
  8. Step 15 · Nice Loops/AICs expert
    Rules out 9 from R7C8.
  9. Step 16 · Nice Loops/AICs expert
    Rules out 1 from R1C4.
  10. Step 18 · ALS-XZ expert
    Rules out 9 from R1C8.
  11. Step 19 · Nice Loops/AICs expert
    Rules out 9 from R2C8.
  12. Step 20 · Cell Forcing Chains expert
    Rules out 9 from R1C1.
  13. Step 24 · Nice Loops/AICs expert
    Rules out 9 from R8C6.
  14. Step 25 · Nice Loops/AICs expert
    Rules out 6 from R5C4.
  15. Step 26 · Nice Loops/AICs expert
    Rules out 9 from R5C5.
  16. Step 27 · WXYZ-Wing expert
    Rules out 6 from R4C6, R5C6.
  17. Step 29 · Empty Rectangle advanced
    Rules out 9 from R1C7.
  18. Step 30 · W-Wing advanced
    Rules out 7 from R2C9, R4C4.
  19. Step 32 · Finned Fish expert
    Rules out 9 from R7C1.
  20. Step 33 · XY-Chain expert
    Rules out 9 from R1C9.
  21. Step 38 · Jellyfish expert
    Rules out 9 from R8C1.
  22. Step 39 · BUG+1 advanced
    Places 6 in R6C9 and rules out 6 from R2C9, R4C9, R5C8, R6C3 and 1 more.

The book

Volume two: 150 new classic 9×9 grids, none repeated from book 1, 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.

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