EXTREMEPUZZLE BOOKS

Extreme Killer Sudoku 2, puzzle 94: 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 94 of 150 in Extreme Killer Sudoku 2
Difficulty
Expert 3 (expert and beyond), from the middle third of the book
Key technique
Remote Pairs
Hard steps
8 of 82 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: Multi-Sector Locking (×3), Advanced Innies (3+ sectors) (×2), Finned Fish, 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 (8)
  1. Step 12 · Multi-Sector Locking advanced
    Rules out 8 from R6C3, R6C7.
  2. Step 13 · Advanced Innies (3+ sectors) advanced
    Places 7 in R6C3 and rules out 7 from R1C3, R3C3, R4C1, R4C2 and 14 more; 2 from R5C2; 3 from R5C2, R5C3, R5C5.
  3. Step 38 · Multi-Sector Locking advanced
    Rules out 9 from R2C9, R3C9.
  4. Step 39 · Advanced Innies (3+ sectors) advanced
    Rules out 4 from R5C1, R5C4, R5C8, R5C9.
  5. Step 42 · Remote Pairs expert
    Rules out 6 from R3C3; 9 from R3C3.
  6. Step 71 · Multi-Sector Locking advanced
    Rules out 8 from R6C9.
  7. Step 73 · Finned Fish expert
    Rules out 1 from R6C8.
  8. Step 74 · Forcing Chains expert
    Rules out 5 from R1C9.

The book

Volume two: 150 new killers, none repeated from book 1. 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.

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