EXTREMEPUZZLE BOOKS

Extreme Killer Sudoku 3, 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.

Puzzle
Killer sudoku, number 26 of 150 in Extreme Killer Sudoku 3
Difficulty
Expert 3 (expert and beyond), from the opening third of the book
Key technique
Coloring/Multi-coloring
Hard steps
16 of 90 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: Coloring/Multi-coloring

Following one digit’s strong links, cells get two colours: one colour is true and the other is false. A cell that sees both colours cannot hold the digit.

Other advanced and expert techniques in this solve: Multi-Sector Locking (×5), Advanced Innies (3+ sectors) (×2), 2-String Kite, Empty Rectangle, Forcing Chains, Remote Pairs, Skyscraper, 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 (16)
  1. Step 10 · Multi-Sector Locking advanced
    Rules out 7 from R4C2, R4C3, R4C7, R4C8 and 5 more.
  2. Step 12 · Advanced Innies (3+ sectors) advanced
    Rules out 3 from R1C3, R8C3; 8 from R4C8, R4C9, R7C4, R8C3 and 1 more; 9 from R4C8, R4C9, R7C4, R8C4.
  3. Step 16 · Coloring/Multi-coloring expert
    Rules out 9 from R4C4.
  4. Step 17 · XYZ-Wing advanced
    Rules out 8 from R5C5, R6C5.
  5. Step 18 · Multi-Sector Locking advanced
    Rules out 9 from R5C5, R6C5, R7C5, R8C5 and 1 more.
  6. Step 19 · Forcing Chains expert
    Rules out 8 from R3C5.
  7. Step 40 · Empty Rectangle advanced
    Rules out 9 from R9C7.
  8. Step 41 · Multi-Sector Locking advanced
    Rules out 9 from R7C6.
  9. Step 42 · Advanced Innies (3+ sectors) advanced
    Places 5 in R8C3 and rules out 4 from R4C8, R4C9, R7C4, R8C4; 5 from R5C3, R6C3, R7C2, R7C3 and 6 more; 2 from R5C4, R6C4, R9C4.
  10. Step 61 · Skyscraper advanced
    Rules out 7 from R5C2.
  11. Step 63 · 2-String Kite advanced
    Rules out 9 from R6C1.
  12. Step 64 · Multi-Sector Locking advanced
    Rules out 7 from R5C3.
  13. Step 65 · Remote Pairs expert
    Rules out 2 from R5C3.
  14. Step 66 · Coloring/Multi-coloring expert
    Rules out 2 from R4C1.
  15. Step 70 · Coloring/Multi-coloring expert
    Rules out 4 from R3C2.
  16. Step 71 · Multi-Sector Locking advanced
    Rules out 4 from R8C1, R9C1.

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.