Einstein's Riddle

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"Einstein's Riddle," also known as the zebra puzzle, is a well-known logic puzzle. It is purported to have been written by Einstein, but there is no evidence that Einstein wrote it (it doesn't seem like the sort of thing Einstein would write, and the earliest sources I've found for the puzzle, from the 1960s and 1970s, mention nothing about Einstein). It is also often stated that 98% of the population cannot solve it, but there is no truth to that either; the average person who can think about the problem logically and has enough patience and time should be able to solve it.

The origins of the puzzle are somewhat obscure. The puzzle appears to have been first published in the 1960s in Life International magazine, under the title "Who Owns the Zebra?", although the publication seems to imply that the puzzle was already popular in various places in the United States at the time. The puzzle caught on after that and became quite popular, being copied and republished in many publications and later online.

Here is the original puzzle; I've reworded it slightly in a few places to resolve ambiguities.

1. There are five houses in a row, each of a different colour (ivory, red, blue, green, and yellow), inhabited by men of different nationalities (English, Spanish, Norwegian, Ukrainian, and Japanese), with different pets (dog, fox, horse, snails, and zebra), favourite drinks (coffee, tea, milk, orange juice, and water) and cigarettes (Old Gold, Kools, Chesterfields, Lucky Strike, and Parliaments).
2. The Englishman lives in the red house.
3. The Spaniard owns the dog.
4. The man living in the green house drinks coffee.
5. The Ukrainian drinks tea.
6. The green house is immediately to the right (your right) of the ivory house.
7. The Old Gold smoker owns snails.
8. Kools are smoked in the yellow house.
9. The man living in the middle house drinks milk.
10. The Norwegian lives in the first house on the left (your left).
11. The man who smokes Chesterfields lives next door to the man with the fox.
12. Kools are smoked next door to the house where the horse is kept.
13. The Lucky Strike smoker drinks orange juice.
14. The Japanese smokes Parliaments.
15. The Norwegian lives next to the blue house.

Who drinks water? And who owns the Zebra?

If you find that you have difficulty with the puzzle, you might find that it helps to draw a diagram or a grid to keep track of all of the information.

The answer can be found on the answers page.

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