EXTREMEPUZZLE BOOKS

Extreme Sudoku 2, puzzle 95: 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 95 of 150 in Extreme Sudoku 2
Difficulty
Expert 5 (expert and beyond), from the middle third of the book
Key technique
XY-Chain
Hard steps
16 of 39 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: XY-Chain

A chain of two-candidate cells, each linked to the next. Whichever way the start cell goes, one end of the chain holds the digit, so cells seeing both ends cannot.

Other advanced and expert techniques in this solve: Nice Loops/AICs (×4), ALS-XZ (×2), W-Wing (×2), Cell Forcing Chains, Empty Rectangle, Finned Fish.

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 (16)
  1. Step 5 · ALS-XZ expert
    Rules out 6 from R1C7.
  2. Step 6 · Cell Forcing Chains expert
    Rules out 4 from R1C7.
  3. Step 9 · Empty Rectangle advanced
    Rules out 4 from R3C6.
  4. Step 11 · ALS-XZ expert
    Rules out 6 from R5C8.
  5. Step 12 · Finned Fish expert
    Rules out 6 from R8C9.
  6. Step 13 · Nice Loops/AICs expert
    Rules out 6 from R2C2.
  7. Step 14 · Nice Loops/AICs expert
    Rules out 6 from R3C9.
  8. Step 15 · Nice Loops/AICs expert
    Rules out 7 from R7C9.
  9. Step 17 · Nice Loops/AICs expert
    Rules out 6 from R7C2.
  10. Step 19 · XY-Chain expert
    Rules out 6 from R2C9.
  11. Step 20 · XY-Chain expert
    Rules out 8 from R5C2.
  12. Step 22 · XY-Chain expert
    Rules out 6 from R1C2.
  13. Step 24 · XY-Chain expert
    Rules out 2 from R4C8, R6C8.
  14. Step 27 · XY-Chain expert
    Rules out 4 from R8C6.
  15. Step 30 · W-Wing advanced
    Rules out 8 from R7C6, R8C1.
  16. Step 35 · W-Wing advanced
    Rules out 2 from R6C6.

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.

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 Sudoku 1 · Extreme Killer Sudoku 1 · Extreme Killer Sudoku 2 · Extreme Sudoku 3 · Extreme Killer Sudoku 3.