EXTREMEPUZZLE BOOKS

Extreme Sudoku 2, puzzle 98: 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 98 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
12 of 41 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 (×3), 2-String Kite, ALS-XZ, Cell Forcing Chains, 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 (12)
  1. Step 9 · 2-String Kite advanced
    Rules out 8 from R3C8.
  2. Step 10 · ALS-XZ expert
    Rules out 3 from R8C7.
  3. Step 11 · Nice Loops/AICs expert
    Rules out 8 from R8C7.
  4. Step 13 · Nice Loops/AICs expert
    Rules out 1 from R3C3.
  5. Step 14 · Nice Loops/AICs expert
    Rules out 1 from R1C9.
  6. Step 15 · Cell Forcing Chains expert
    Rules out 8 from R1C3.
  7. Step 22 · XY-Chain expert
    Rules out 5 from R7C1.
  8. Step 25 · Finned Fish expert
    Rules out 4 from R2C9.
  9. Step 26 · XY-Chain expert
    Rules out 4 from R2C5, R9C2.
  10. Step 29 · XY-Chain expert
    Rules out 5 from R4C1.
  11. Step 32 · XY-Chain expert
    Rules out 3 from R1C9, R3C4.
  12. Step 35 · XY-Chain expert
    Rules out 4 from R9C8.

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.