Extreme Killer Sudoku 3, puzzle 120: 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: Finned Fish
An X-Wing or Swordfish with one extra candidate (the fin). Cells that are in the fish pattern and also see the fin lose the digit.
Other advanced and expert techniques in this solve: Multi-Sector Locking (×2), Advanced Innies (3+ sectors), Coloring/Multi-coloring, Empty Rectangle, 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 17 · Multi-Sector Locking advanced
Rules out 6 from R1C7, R1C8; 9 from R1C7, R1C8; 1 from R9C7. - Step 44 · Multi-Sector Locking advanced
Rules out 7 from R5C9. - Step 45 · Advanced Innies (3+ sectors) advanced
Places 9 in R5C6 and rules out 9 from R5C1, R5C2, R6C6. - Step 47 · Finned Fish expert
Rules out 9 from R9C1. - Step 49 · Forcing Chains expert
Rules out 3 from R1C9, R2C9; 4 from R1C9, R2C9. - Step 71 · Empty Rectangle advanced
Rules out 8 from R7C5. - Step 74 · Coloring/Multi-coloring expert
Rules out 1 from R3C3, R4C2.
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.