Grid technique
How to Complete a Logic Grid Without Guessing
If you feel forced to guess, the missing step is usually not another clue—it is a consequence of a mark already on the grid. Slow down, propagate every confirmed fact and combine constraints deliberately.
Complete the consequences of every match
When a row receives a confirmed match, every other cell in that row and the corresponding column becomes impossible. Apply those exclusions immediately across all linked mini-grids. Many stalled puzzles restart when one old match is fully propagated.
- Audit each confirmed mark row by row.
- Check the same relationship in the mirrored grid.
- Do not leave a completed row with blank alternatives.
Translate compound clues
A clue may connect several categories indirectly: the person before the gardener did not carry the ledger. Write the ordering rule, the occupation restriction and the object exclusion separately before combining them. This reduces the chance of adding a conclusion the wording never supported.
- Separate OR from AND.
- Treat ‘either A or B’ as unresolved until another clue decides it.
- Keep relative order distinct from immediate adjacency.
Find forced pairs and triples
If two people can only occupy two times, those times are reserved for that pair even before you know which person takes which. Eliminate those times from every other person. The same locked-set principle works with three candidates and three options.
- Circle unresolved locked sets.
- Use the reservation to eliminate outside candidates.
- Do not arbitrarily assign members within the set.
Use a controlled contradiction test
Only when direct propagation is exhausted should you test a branch. Copy the unresolved state, assume one candidate match and follow its necessary consequences. A contradiction rejects that branch; an incomplete but consistent branch proves nothing yet. This is logical testing, not guessing.