EXTREMEPUZZLE BOOKS

Extreme Sudoku 1, puzzle 136: 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 136 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
28 of 54 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 (×8), 2-String Kite (×3), WXYZ-Wing (×3), XY-Chain (×2), Cell Forcing Chains.

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 28)
  1. Step 6 · ALS-XZ expert
    Rules out 2 from R4C1.
  2. Step 8 · ALS-XZ expert
    Rules out 4 from R2C9.
  3. Step 10 · 2-String Kite advanced
    Rules out 5 from R4C1.
  4. Step 11 · Nice Loops/AICs expert
    Rules out 8 from R7C6.
  5. Step 12 · 2-String Kite advanced
    Rules out 8 from R8C8.
  6. Step 13 · Cell Forcing Chains expert
    Rules out 7 from R2C6.
  7. Step 16 · ALS-XZ expert
    Rules out 7 from R3C8.
  8. Step 17 · ALS-XZ expert
    Rules out 6 from R8C7.
  9. Step 19 · ALS-XZ expert
    Rules out 2 from R7C9.
  10. Step 20 · Nice Loops/AICs expert
    Rules out 3 from R1C3.
  11. Step 21 · Nice Loops/AICs expert
    Rules out 5 from R4C8.
  12. Step 22 · Nice Loops/AICs expert
    Rules out 7 from R5C1.
  13. Step 23 · Nice Loops/AICs expert
    Rules out 6 from R5C3.
  14. Step 24 · Nice Loops/AICs expert
    Rules out 3 from R2C2.
  15. Step 25 · Nice Loops/AICs expert
    Rules out 3 from R5C1.
  16. Step 26 · WXYZ-Wing expert
    Rules out 6 from R8C1.
  17. Step 28 · ALS-XZ expert
    Rules out 3 from R1C2.
  18. Step 31 · WXYZ-Wing expert
    Rules out 7 from R9C1.
  19. Step 32 · ALS-XZ expert
    Rules out 3 from R9C2.
  20. Step 33 · Nice Loops/AICs expert
    Rules out 7 from R2C2.
  21. Step 34 · Nice Loops/AICs expert
    Rules out 7 from R5C8.
  22. Step 35 · Nice Loops/AICs expert
    Rules out 8 from R8C1.
  23. Step 38 · Nice Loops/AICs expert
    Rules out 7 from R2C7.
  24. Step 40 · ALS-XZ expert
    Rules out 5 from R4C2.

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.