EXTREMEPUZZLE BOOKS

Extreme Killer Sudoku 3, 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.

Puzzle
Killer sudoku, number 79 of 150 in Extreme Killer Sudoku 3
Difficulty
Expert 2 (expert and beyond), from the middle third of the book
Key technique
Remote Pairs
Hard steps
11 of 70 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: 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) (×3), Multi-Sector Locking (×3), Empty Rectangle (×2), 2-String Kite, 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 (11)
  1. Step 13 · Multi-Sector Locking advanced
    Rules out 9 from R1C3, R5C3, R6C3.
  2. Step 14 · Advanced Innies (3+ sectors) advanced
    Rules out 6 from R1C3, R1C5; 5 from R1C5; 7 from R1C5.
  3. Step 24 · Multi-Sector Locking advanced
    Rules out 9 from R1C1, R1C2, R1C4, R2C8 and 4 more.
  4. Step 27 · Advanced Innies (3+ sectors) advanced
    Rules out 1 from R1C5; 2 from R1C5.
  5. Step 28 · Remote Pairs expert
    Rules out 3 from R9C7, R9C8.
  6. Step 35 · 2-String Kite advanced
    Rules out 5 from R1C6.
  7. Step 36 · Empty Rectangle advanced
    Rules out 5 from R1C9.
  8. Step 38 · Forcing Chains expert
    Rules out 5 from R1C3, R2C6, R2C9, R3C4 and 14 more; 1 from R1C4, R2C4, R6C4, R7C4 and 6 more; 6 from R1C7, R1C8, R1C9, R2C5 and 15 more.
  9. Step 43 · Empty Rectangle advanced
    Rules out 4 from R3C3.
  10. Step 45 · Multi-Sector Locking advanced
    Rules out 8 from R1C8, R6C8, R8C8; 4 from R2C8, R3C8, R4C8, R5C8.
  11. Step 49 · Advanced Innies (3+ sectors) advanced
    Places 3 in R1C5 and rules out 3 from R1C1, R1C2, R1C3, R1C4 and 10 more; 2 from R6C2; 8 from R6C2.

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

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.