Math · Exploration
The Zebra Puzzle
Who drinks water, and who owns the zebra?
Five houses, five attributes
Five adjacent houses have different colours. Their occupants have different nationalities, pets, drinks, and cigarette brands. Use the clues to determine the complete arrangement.
- The Englishman lives in the red house; the Spaniard owns the dog; and the Ukrainian drinks tea.
- Coffee is drunk in the green house, which is immediately to the right of the ivory house.
- The Old Gold smoker owns snails, and Kools are smoked in the yellow house.
- Milk is drunk in the middle house, while the Norwegian lives in the first house.
- The Chesterfields smoker lives beside the fox owner; Kools are smoked beside the horse owner.
- The Lucky Strike smoker drinks orange juice, and the Japanese smokes Parliaments.
- The Norwegian lives beside the blue house.
Make your deduction
Work through the clues before making your final prediction.
Choose both answers when you are ready.
Start with the fixed houses
The Norwegian is in house 1, so the clue about the blue house fixes house 2 as blue. House 1 cannot be red, green, or ivory, leaving yellow. Kools are therefore smoked in house 1. Those early deductions make the neighbouring-horse clue useful and gradually narrow the remaining possibilities.
Constraint satisfaction
This is a constraint satisfaction problem. Each category is a permutation of five values, and each clue removes incompatible permutations. A person can solve it by filling a logic grid; a program can solve it by searching possible assignments and rejecting any that violate a clue.
Source
This version follows the 1962 Life International puzzle.