Clues
Tap a clue to cross it offHouses 1–4 stand in a row, left to right. Each house has one color, pet, drink and job.
Mark every house's color, pet, drink and job with ✓ to close the case.
The Machine
Algorithm X · exact coverThe same puzzle as an exact cover matrix: every row puts one value in one house, and every column has to be covered exactly once. The left of, next to and same house clues are checked during the search, and it backtracks when one breaks.
covered column
chosen row
backtrack
ruled out by a clue
Ready.
Steps0
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