Thermo · Medium

Locked Candidates in Thermo Sudoku

When a house can place a digit only where it meets another house, the digit is eliminated from the rest of that other house.

The idea

If every cell in a house that can take a digit also lies in a second house, the digit must go there, and the rest of the second house cannot have it.

On a Thermo board this works exactly as in Classic. The examples are from Thermo puzzles on this site.

Worked examples

A position from a real Thermo puzzle on this site. Step through it: the board lights what each step talks about, and the arrows show what rules what out.

A box and a line

Medium puzzle · Locked Candidates

In box 1, find every cell that can still take 8.

Step 1 of 4Step 2 of 4Step 3 of 4Step 4 of 4

Where it fits

MediumLocked Candidates is a Medium technique: Medium Thermo puzzles are the first to need it.

The Classic Locked Candidates lesson teaches it on a plain 9×9 board. The Thermo overview explains the rule and the levels.

Locked Candidates in the other styles: Sudoku X, Jigsaw, Windoku, Arrow, Kropki.

Try it on a Medium Thermo puzzle. Next Step points it out when it is the move.

The worked examples, every step

A box and a line

Medium Thermo puzzle · Locked Candidates

  1. In box 1, find every cell that can still take 8.
  2. All of them (R2C3, R3C3) are also in column 3. Box 1 must have an 8 somewhere in those cells, so the rest of column 3 cannot. The arrows point to the cells that lose 8.
  3. Eliminate 8 from R9C3.
  4. Done: 8 is eliminated from R9C3.

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