Einstein’s Zebra

Let’s begin with a bit of fun, shall we? There is a fairly well-known puzzle out there known as “Einstein’s Puzzle,” “Einstein’s Riddle,” and the “Zebra Puzzle.” It has been attributed to both Einstein and Lewis Carroll, though the likelihood that either of them actually created it is slim. The general idea of the thing is you are presented with five different (presumably fictitious) men. Each one is of a different nationality, has a different type of animal for a pet, enjoys a different type of drink, and so on–no similarities exist between any of them.

You’re given a list of facts about the men, such as “The Englishman lives in the red house.” With this finite list of information, you are then asked to determine which of the five men owns the pet zebra. There are variations on the puzzle, but the concept stays the same.

Per Wikipedia–the solution is on there; fair warning!–the following version of the puzzle appeared in Life International in 1962:

There are five houses.
The Englishman lives in the red house.
The Spaniard owns the dog.
Coffee is drunk in the green house.
The Ukrainian drinks tea.
The green house is immediately to the right of the ivory house.
The Old Gold smoker owns snails.
Kools are smoked in the yellow house.
Milk is drunk in the middle house.
The Norwegian lives in the first house.
The man who smokes Chesterfields lives in the house next to the man with the fox.
Kools are smoked in the house next to the house where the horse is kept.
The Lucky Strike smoker drinks orange juice.
The Japanese smokes Parliaments.
The Norwegian lives next to the blue house.

Now, who drinks water? Who owns the zebra?

In the interest of clarity, it must be added that each of the five houses is painted a different color, and their inhabitants are of different national extractions, own different pets, drink different beverages and smoke different brands of American cigarettes. One other thing: in statement 6, right means your right.

So, what do you think? In an (admittedly, old-looking) post, a slightly different version of the puzzle is broken down as a “simple constraint satisfaction problem.” Frankly, that term alone tells me that there’s nothing simple about it. What follows is a bunch of what appears to be some sort of computer language and math–which I don’t mind–but when I worked on the puzzle, I used a table. It’s been a while, but it probably looked something like this:

House Number (left to right)	Nationality	House Color	Pet	Drink	Cigarette
1 2 3 4 5	English Spanish Japanese Norwegian Ukrainian	Red Green Yellow Blue Ivory	Horse Snails Dog Fox Zebra	OJ Tea Milk Water Coffee	Lucky Strike Parliament Old Gold Chesterfield Kool
1 2 3 4 5	English Spanish Japanese Norwegian Ukrainian	Red Green Yellow Blue Ivory	Horse Snails Dog Fox Zebra	OJ Tea Milk Water Coffee	Lucky Strike Parliament Old Gold Chesterfield Kool
1 2 3 4 5	English Spanish Japanese Norwegian Ukrainian	Red Green Yellow Blue Ivory	Horse Snails Dog Fox Zebra	OJ Tea Milk Water Coffee	Lucky Strike Parliament Old Gold Chesterfield Kool
1 2 3 4 5	English Spanish Japanese Norwegian Ukrainian	Red Green Yellow Blue Ivory	Horse Snails Dog Fox Zebra	OJ Tea Milk Water Coffee	Lucky Strike Parliament Old Gold Chesterfield Kool
1 2 3 4 5	English Spanish Japanese Norwegian Ukrainian	Red Green Yellow Blue Ivory	Horse Snails Dog Fox Zebra	OJ Tea Milk Water Coffee	Lucky Strike Parliament Old Gold Chesterfield Kool

Using a process of elimination, I was able to gradually eliminate variables to get to a solution. I know it isn’t the most elegant method, but you have to go with what works for you. So, what do you think? Want to give it a try? If this is old hat to you, how about some other logic problems, then? Let me know how it goes!

-h