Killer Sudoku rules and puzzles

The case notes

Compare two Killer cages through their shared row

These two cages do not overlap. One stays in the top row; the other reaches down into the row below. Their digits can still affect each other. Watch a worked example, then try the idea in a puzzle.

Put it into practice

Two cages, one shared row

These two cages do not overlap. One stays in the top row; the other reaches down into the row below. Their digits can still affect each other.

3-cage: {1, 2} · 4-cage: {1, 3}

The three-cage holds one and two. The four-cage holds one and three: two plus two repeats a digit, so it is not allowed.

Row one already has the 1

The top cell of the four-cage shares a row with both cells of the three-cage. One is already somewhere in that row, so this top cell cannot be one.

3 above 1

That puts three at the top of the four-cage and one below it. Compare what the cages must contain, then look at which of their cells see each other.

Read the transcript

These two cages do not overlap. One stays in the top row; the other reaches down into the row below. Their digits can still affect each other. The three-cage holds one and two. The four-cage holds one and three: two plus two repeats a digit, so it is not allowed. The top cell of the four-cage shares a row with both cells of the three-cage. One is already somewhere in that row, so this top cell cannot be one. That puts three at the top of the four-cage and one below it. Compare what the cages must contain, then look at which of their cells see each other.

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