EXTREMEPUZZLE BOOKS

Extreme Sudoku 1, puzzle 114: 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 114 of 150 in Extreme Sudoku 1
Difficulty
Expert 5 (expert and beyond), from the final, hardest third of the book
Key technique
Nice Loops/AICs
Hard steps
25 of 48 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 (×3), XY-Chain (×2), Cell Forcing Chains, Finned Fish, W-Wing, X-Wing/Swordfish, 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 (24 of 25)
  1. Step 5 · ALS-XZ expert
    Rules out 2 from R5C2.
  2. Step 6 · Nice Loops/AICs expert
    Rules out 9 from R8C3.
  3. Step 7 · Cell Forcing Chains expert
    Rules out 7 from R3C2.
  4. Step 11 · Nice Loops/AICs expert
    Rules out 3 from R4C3.
  5. Step 12 · Nice Loops/AICs expert
    Rules out 1 from R6C2.
  6. Step 13 · Nice Loops/AICs expert
    Rules out 1 from R5C9.
  7. Step 15 · Nice Loops/AICs expert
    Rules out 8 from R4C9.
  8. Step 16 · ALS-XZ expert
    Rules out 5 from R4C8.
  9. Step 17 · Nice Loops/AICs expert
    Rules out 7 from R6C7.
  10. Step 19 · Nice Loops/AICs expert
    Rules out 4 from R7C8.
  11. Step 20 · Nice Loops/AICs expert
    Rules out 6 from R8C3.
  12. Step 21 · Nice Loops/AICs expert
    Rules out 9 from R7C4.
  13. Step 22 · Nice Loops/AICs expert
    Rules out 8 from R4C8.
  14. Step 26 · Nice Loops/AICs expert
    Rules out 6 from R9C7.
  15. Step 27 · Nice Loops/AICs expert
    Rules out 4 from R6C8.
  16. Step 28 · Nice Loops/AICs expert
    Rules out 4 from R5C7.
  17. Step 30 · Finned Fish expert
    Rules out 4 from R6C4, R6C6.
  18. Step 31 · ALS-XZ expert
    Rules out 4 from R7C4.
  19. Step 32 · Nice Loops/AICs expert
    Rules out 4 from R7C5.
  20. Step 34 · XY-Wing advanced
    Rules out 5 from R4C9.
  21. Step 35 · W-Wing advanced
    Rules out 5 from R5C1, R6C8.
  22. Step 37 · X-Wing/Swordfish advanced
    Rules out 3 from R6C2, R6C6, R7C6.
  23. Step 38 · Nice Loops/AICs expert
    Rules out 6 from R9C3.
  24. Step 41 · XY-Chain expert
    Rules out 9 from R8C4.

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.

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