Extreme Killer Sudoku 1, puzzle 26: 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: 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 (4)
- Step 16 · Multi-Sector Locking advanced
Rules out 9 from R1C3; 1 from R2C3. - Step 46 · Remote Pairs expert
Rules out 7 from R4C5; 8 from R4C5. - Step 49 · Coloring/Multi-coloring expert
Rules out 5 from R9C8. - Step 50 · Forcing Chains expert
Rules out 4 from R2C9, R6C6, R7C9, R9C9; 2 from R3C5, R7C5, R8C5; 5 from R3C8, R6C9, R8C9.
The book
No starting digits at all: just cages and their totals. Sudoku rules, plus arithmetic, plus a lot of nerve.
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 Sudoku 1 · Extreme Sudoku 2 · Extreme Killer Sudoku 2 · Extreme Sudoku 3 · Extreme Killer Sudoku 3.