Extreme Killer Sudoku 2, puzzle 79: 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), Forcing Chains, Multi-Sector Locking, Skyscraper.
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 30 · Multi-Sector Locking advanced
Rules out 9 from R6C9; 4 from R7C7. - Step 32 · Advanced Innies (3+ sectors) advanced
Places 3 in R7C5 and rules out 3 from R1C5, R2C5, R5C5, R6C5 and 8 more. - Step 52 · Skyscraper advanced
Rules out 6 from R8C8. - Step 53 · Remote Pairs expert
Rules out 7 from R6C7. - Step 55 · Forcing Chains expert
Rules out 2 from R1C5.
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.