Extreme Killer Sudoku 3, puzzle 43: 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: Remote Pairs
A chain of cells that all hold the same pair alternates between the two digits. Cells that see both ends of an odd-length link cannot hold either digit.
Other advanced and expert techniques in this solve: Advanced Innies (3+ sectors), Coloring/Multi-coloring, Forcing Chains, Multi-Sector Locking.
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 (5)
- Step 17 · Advanced Innies (3+ sectors) advanced
Places 1 in R1C3, 4 in R1C4, 3 in R8C5, 4 in R9C5 and rules out 1 from R1C1, R1C2, R1C5, R1C6 and 13 more; 4 from R1C1, R1C2, R1C5, R1C6 and 26 more; 3 from R1C5, R2C5, R6C5, R7C4 and 12 more. - Step 54 · Multi-Sector Locking advanced
Rules out 8 from R4C2. - Step 62 · Remote Pairs expert
Rules out 2 from R2C2; 4 from R2C2. - Step 65 · Coloring/Multi-coloring expert
Rules out 7 from R8C3. - Step 66 · Forcing Chains expert
Rules out 5 from R1C9.
The book
Volume three: 150 new killers, none repeated from books 1 or 2. 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 Killer Sudoku 2 · Extreme Sudoku 3.