EXTREMEPUZZLE BOOKS

Extreme Killer Sudoku 3, puzzle 83: 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 83 of 150 in Extreme Killer Sudoku 3
Difficulty
Expert 3 (expert and beyond), from the middle third of the book
Key technique
Forcing Chains
Hard steps
9 of 88 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: Forcing Chains

Try each candidate of one cell in turn. Every choice leads to the same result, so that result must be true.

Other advanced and expert techniques in this solve: Advanced Innies (3+ sectors) (×3), 2-String Kite, Coloring/Multi-coloring, Empty Rectangle, Multi-Sector Locking, Remote Pairs.

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 6 · Multi-Sector Locking advanced
    Rules out 1 from R2C2, R3C2, R4C1, R4C3 and 5 more.
  2. Step 7 · Advanced Innies (3+ sectors) advanced
    Rules out 1 from R2C5, R3C1, R5C9, R7C8; 2 from R2C5, R5C2, R7C8; 3 from R2C5, R5C2, R5C5.
  3. Step 10 · Forcing Chains expert
    Rules out 7 from R6C2.
  4. Step 22 · Advanced Innies (3+ sectors) advanced
    Places 5 in R7C8 and rules out 5 from R1C8, R2C8, R3C8, R4C8 and 15 more; 3 from R5C1, R6C1.
  5. Step 27 · Empty Rectangle advanced
    Rules out 1 from R7C6.
  6. Step 56 · 2-String Kite advanced
    Rules out 9 from R5C7.
  7. Step 57 · Advanced Innies (3+ sectors) advanced
    Rules out 7 from R5C5.
  8. Step 58 · Remote Pairs expert
    Rules out 5 from R4C4.
  9. Step 59 · Coloring/Multi-coloring expert
    Rules out 9 from R4C6.

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.