EXTREMEPUZZLE BOOKS

Extreme Sudoku 2, puzzle 60: 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 60 of 150 in Extreme Sudoku 2
Difficulty
Expert 6 (expert and beyond), from the middle third of the book
Key technique
Nice Loops/AICs
Hard steps
25 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: 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 (×6), 2-String Kite (×2), Cell Forcing Chains, Finned Fish, WXYZ-Wing, X-Wing/Swordfish, 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 (24 of 25)
  1. Step 6 · 2-String Kite advanced
    Rules out 3 from R1C6.
  2. Step 7 · 2-String Kite advanced
    Rules out 4 from R5C6.
  3. Step 8 · Finned Fish expert
    Rules out 5 from R5C6.
  4. Step 9 · WXYZ-Wing expert
    Rules out 8 from R5C9.
  5. Step 10 · Nice Loops/AICs expert
    Rules out 8 from R9C3.
  6. Step 12 · Nice Loops/AICs expert
    Rules out 8 from R8C3.
  7. Step 13 · Nice Loops/AICs expert
    Rules out 9 from R3C8.
  8. Step 15 · Nice Loops/AICs expert
    Rules out 3 from R6C6.
  9. Step 16 · Cell Forcing Chains expert
    Rules out 8 from R1C2.
  10. Step 20 · ALS-XZ expert
    Rules out 6 from R4C3.
  11. Step 22 · ALS-XZ expert
    Rules out 5 from R6C4.
  12. Step 23 · ALS-XZ expert
    Rules out 2 from R8C5.
  13. Step 25 · ALS-XZ expert
    Rules out 5 from R5C4.
  14. Step 26 · ALS-XZ expert
    Rules out 7 from R8C9.
  15. Step 27 · Nice Loops/AICs expert
    Rules out 1 from R5C6.
  16. Step 29 · Nice Loops/AICs expert
    Rules out 1 from R4C1.
  17. Step 30 · Nice Loops/AICs expert
    Rules out 8 from R8C1.
  18. Step 33 · Nice Loops/AICs expert
    Rules out 5 from R5C9.
  19. Step 34 · Nice Loops/AICs expert
    Rules out 4 from R6C6.
  20. Step 36 · X-Wing/Swordfish advanced
    Rules out 5 from R4C8, R8C6, R8C8.
  21. Step 37 · XY-Chain expert
    Rules out 2 from R8C9.
  22. Step 38 · ALS-XZ expert
    Rules out 5 from R4C5.
  23. Step 39 · Nice Loops/AICs expert
    Rules out 2 from R4C5.
  24. Step 40 · Nice Loops/AICs expert
    Rules out 5 from R5C5.

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.