EXTREMEPUZZLE BOOKS

Extreme Killer Sudoku 3, puzzle 10: 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 10 of 150 in Extreme Killer Sudoku 3
Difficulty
Expert 4 (expert and beyond), from the opening third of the book
Key technique
Remote Pairs
Hard steps
9 of 93 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) (×2), 2-String Kite, Coloring/Multi-coloring, Finned Fish, Forcing Chains, XY-Wing, XYZ-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 (9)
  1. Step 20 · Advanced Innies (3+ sectors) advanced
    Rules out 6 from R5C6, R6C2, R6C6; 7 from R5C6, R6C6, R7C6; 3 from R6C2.
  2. Step 24 · XY-Wing advanced
    Rules out 9 from R4C2, R5C2.
  3. Step 26 · Remote Pairs expert
    Rules out 8 from R6C4; 9 from R6C4.
  4. Step 27 · Coloring/Multi-coloring expert
    Rules out 7 from R3C5.
  5. Step 28 · Forcing Chains expert
    Rules out 5 from R2C1.
  6. Step 44 · Advanced Innies (3+ sectors) advanced
    Places 2 in R7C3 and rules out 2 from R4C3, R5C3, R7C1; 5 from R5C6, R6C6.
  7. Step 72 · XYZ-Wing advanced
    Rules out 7 from R4C8.
  8. Step 74 · 2-String Kite advanced
    Rules out 7 from R2C7.
  9. Step 75 · Finned Fish expert
    Rules out 7 from R3C7.

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.