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There’s this puzzle called Einstein’s Riddle, also known as Zebra Puzzle, which is said to have been written by Albert Einstein as a boy, and the common claim is that 98% of the world’s population wouldn’t be able to solve it.

There is no known evidence that Einstein authored the puzzle, and there are several versions of it. One such puzzle goes like this:

There are five houses painted in five different colors. There are five different nationalities. Each drinks a different drink, smokes a different cigar, and keeps a different pet.

Given rules:

1. The Brit lives in a red house.
2. The Swede keeps a dog.
3. The Dane drinks tea.
4. The green house is on the immediate left of the white house.
5. The owner of the green house drinks coffee.
6. The person who smokes Pall Mall keeps a bird.
7. The owner of the yellow house smokes Dunhill.
8. The man living in the center house drinks milk.
9. The Norwegian lives in the first house.
10. The man who smokes Blends lives next to one who keeps a cat.
11. The man who keeps a horse lives next to a Dunhill smoker.
12. The man who smokes Blue Master drinks beer.
13. The German smokes Prince.
14. The Norwegian lives next to the blue house.
15. The man who smokes Blends has a neighbor who drinks water.

The question is who owns the fish?

There isn’t any direct evidence that only the top 2% of the world’s population would be able to solve it. Give it a try. This is a logic puzzle. No tricks.

While this puzzle may seem fairly similar to a game of Sudoku, it distinguishes the logical mathematician with a logical non-mathematician. I agree that maths reveals a person’s logical thinking capability, but logic can stand on its own.

Sarcasm is only funny when it is logical.

While Sudoku can drive some to commit seppuku, this game of Zebra Puzzle is just as challenging and less lethal to the delicate minds. Nevertheless, just as interesting.

Here’s the solution. There may be other ways to solve the problem, this is mine. Based on 1, 4, 5, 8, 9 and 14, we get:

Norwegian		Brit
	Blue	Red	Green	White
		Milk	Coffee

Rule 9 and 14 are immediate known constants. We know green house is in column 4 because column 2 is populated by blue house, and based on rule 8 column 3 must be a milk drinker, whereas rule 5 tells us that green house drinks coffee.

Next, based on rule 3, 7, 10, 11, 12 and 15 we can derive the following:

Norwegian	Dane	Brit
Yellow	Blue	Red	Green	White
Water	Tea	Milk	Coffee	Beer
Dunhill	Blends			Blue Master
Cat	Horse

The reason why the Dane goes into column 2 instead of column 5 is because rule 12 suggests a beer drinker and Blue Master smoker with no neighboring water drinker. Based on rule 15, someone has to smoke Blends and has a neighbor who drinks water. Then since all the other columns have a known beverage drinker, the Norwegian must be the water drinker. And a Dane fitting rule 15 fits rule 10 too.

You may ask then, why doesn’t rule 10 fit column 3? It’s because rule 6 states that Pall Mall and bird goes together and the only column that would fit both rules is column 3. Next, we study rule 2, 6, and 13.

Norwegian	Dane	Brit	German	Swede
Yellow	Blue	Red	Green	White
Water	Tea	Milk	Coffee	Beer
Dunhill	Blends	Pall Mall	Prince	Blue Master
Cat	Horse	Bird		Dog

Pall Mall and bird goes hand in hand, so column 3 is the place where it would fit. Rule 13 would only fit in column 4 thus making it German and leaves us column 5 with rule 2. Therefore, the answer to the question who owns the fish is the German.

Sometimes, I find it hard to explain logic in a verbal sentence. Especially when explaining program’s codes. A single logical thought, translated, expands into multiple sentences in any form of verbal communication in any human language.

In my personal opinion, the best conveyor of logic is still and will always be a computer programming syntax or a mathematical equation; easy to read, hard to verbalize.