EXTREMEPUZZLE BOOKS

Extreme Killer Sudoku 3, puzzle 62: 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.

Puzzle
Killer sudoku, number 62 of 150 in Extreme Killer Sudoku 3
Difficulty
Expert 2 (expert and beyond), from the middle third of the book
Key technique
Finned Fish
Hard steps
11 of 89 steps need an advanced or expert technique

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: 2-String Kite (×3), Advanced Innies (3+ sectors) (×2), Multi-Sector Locking (×2), Forcing Chains, XY-Wing.

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 (11)
  1. Step 13 · Advanced Innies (3+ sectors) advanced
    Rules out 1 from R5C1, R5C5, R5C8; 2 from R5C1, R5C2, R5C5, R5C8; 4 from R5C6, R9C5.
  2. Step 15 · Forcing Chains expert
    Rules out 4 from R5C9, R6C9, R8C8, R8C9 and 2 more; 7 from R7C9, R8C8, R8C9, R9C8 and 1 more; 5 from R8C8, R8C9, R9C8, R9C9.
  3. Step 36 · Multi-Sector Locking advanced
    Rules out 5 from R6C4, R6C5; 1 from R9C5.
  4. Step 42 · Multi-Sector Locking advanced
    Rules out 8 from R7C4, R8C4, R8C5, R9C4.
  5. Step 43 · Advanced Innies (3+ sectors) advanced
    Rules out 3 from R5C3; 6 from R5C3, R5C4; 9 from R5C3, R5C4, R5C9.
  6. Step 69 · XY-Wing advanced
    Rules out 4 from R3C2.
  7. Step 70 · 2-String Kite advanced
    Rules out 4 from R8C1.
  8. Step 71 · 2-String Kite advanced
    Rules out 5 from R1C3.
  9. Step 72 · 2-String Kite advanced
    Rules out 6 from R2C8.
  10. Step 73 · Finned Fish expert
    Rules out 2 from R2C2, R3C2.
  11. Step 75 · Finned Fish expert
    Rules out 9 from R2C2, R3C2.

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.

On Amazon from 15 Dec About the book

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More step-by-step solutions: Extreme Sudoku 1 · Extreme Killer Sudoku 1 · Extreme Sudoku 2 · Extreme Killer Sudoku 2 · Extreme Sudoku 3.