Extreme Killer Sudoku 2, puzzle 41: 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: Coloring/Multi-coloring
Following one digit’s strong links, cells get two colours: one colour is true and the other is false. A cell that sees both colours cannot hold the digit.
Other advanced and expert techniques in this solve: Multi-Sector Locking (×2), Advanced Innies (3+ sectors), Forcing Chains.
Every move above the basics is listed on the killer sudoku techniques page, each with a one-sentence explanation and worked examples from the books.
The hard steps, in text (7)
- Step 10 · Multi-Sector Locking advanced
Rules out 1 from R7C7, R9C7. - Step 11 · Advanced Innies (3+ sectors) advanced
Places 3 in R7C4 and rules out 3 from R1C4, R4C4, R5C4, R6C4 and 13 more. - Step 18 · Coloring/Multi-coloring expert
Rules out 9 from R6C4. - Step 19 · Forcing Chains expert
Rules out 2 from R6C1; 3 from R6C1. - Step 44 · Multi-Sector Locking advanced
Rules out 9 from R2C6. - Step 45 · Coloring/Multi-coloring expert
Rules out 3 from R2C7. - Step 46 · Coloring/Multi-coloring expert
Rules out 8 from R8C7.
The book
Volume two: 150 new killers, none repeated from book 1. No starting digits, just cages and their totals, 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.
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 Sudoku 2 · Extreme Sudoku 3 · Extreme Killer Sudoku 3.