Extreme Sudoku 1, puzzle 46: 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.
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: ALS-XZ (×2), 2-String Kite, Cell Forcing Chains, Nice Loops/AICs, WXYZ-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 (10)
- Step 3 · 2-String Kite advanced
Rules out 7 from R3C6. - Step 4 · ALS-XZ expert
Rules out 5 from R8C4, R8C6. - Step 6 · Nice Loops/AICs expert
Rules out 8 from R5C9. - Step 7 · Cell Forcing Chains expert
Rules out 3 from R1C4. - Step 10 · ALS-XZ expert
Rules out 7 from R3C1, R8C3, R9C3. - Step 15 · XY-Chain expert
Rules out 7 from R3C8. - Step 17 · WXYZ-Wing expert
Rules out 4 from R1C9. - Step 21 · XY-Chain expert
Rules out 3 from R1C6, R6C5. - Step 24 · XY-Chain expert
Rules out 4 from R3C7, R7C8. - Step 26 · XY-Chain expert
Rules out 9 from R1C9, R3C6.
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.
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.