EXTREMEPUZZLE BOOKS

Extreme Killer Sudoku 1, puzzle 95: 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 95 of 150 in Extreme Killer Sudoku 1
Difficulty
Expert 3 (expert and beyond), from the middle third of the book
Key technique
Remote Pairs
Hard steps
10 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: 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 (×5), Advanced Innies (3+ sectors), Empty Rectangle, 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 (10)
  1. Step 11 · Multi-Sector Locking advanced
    Rules out 8 from R3C9; 4 from R4C2, R4C3.
  2. Step 12 · Advanced Innies (3+ sectors) advanced
    Places 7 in R8C4 and rules out 7 from R1C4, R2C4, R3C4, R4C4 and 12 more.
  3. Step 25 · Multi-Sector Locking advanced
    Rules out 3 from R3C1; 5 from R3C2.
  4. Step 29 · Multi-Sector Locking advanced
    Rules out 9 from R2C4.
  5. Step 32 · Remote Pairs expert
    Rules out 2 from R6C2; 6 from R6C2.
  6. Step 33 · Multi-Sector Locking advanced
    Rules out 2 from R7C1, R8C1, R9C1; 6 from R9C1.
  7. Step 50 · Finned Fish expert
    Rules out 9 from R3C9.
  8. Step 51 · Forcing Chains expert
    Rules out 4 from R1C2.
  9. Step 63 · Empty Rectangle advanced
    Rules out 3 from R5C8.
  10. Step 64 · Multi-Sector Locking advanced
    Rules out 5 from R1C7, R2C7.

The book

No starting digits at all: just cages and their totals. Sudoku rules, plus arithmetic, plus a lot of nerve.

150 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 Sudoku 2 · Extreme Killer Sudoku 2 · Extreme Sudoku 3 · Extreme Killer Sudoku 3.