Background:
There are five houses lined up next to each other along a street. Each house is a different color, and each homeowner is of a different nationality, drinks a different beverage, smokes a different brand of cigar, and owns a different pet.
If these variables can never repeat from house to house, which homeowner has a pet fish? You should be able to figure out the answer based on these 15 clues:
The Englishman lives in the house with red walls.
The Swede keeps dogs.
The Dane drinks tea.
The house with green walls is just to the left of the house with white walls.
The owner of the house with green walls drinks coffee.
The man who smokes Pall Mall keeps birds.
The owner of the house with yellow walls smokes Dunhills.
The man in the center house drinks milk.
The Norwegian lives in the first house.
The Blend smoker has a neighbor who keeps cats.
The man who smokes Blue Masters drinks beer.
The man who keeps horses lives next to the Dunhill smoker.
The German smokes Prince.
The Norwegian lives next to the house with blue walls.
The Blend smoker has a neighbor who drinks water.
The origin of "Einstein's Riddle" is unclear, but it's often called this because it's said to have been created by Albert Einstein. However, there's no evidence that Einstein wrote it.
Explanation
"Einstein's Riddle" is actually a logic puzzle that goes by many names, including the Zebra Puzzle.
There are many versions of the puzzle.
A version of the puzzle was published in Life International magazine in 1962.
The puzzle involves a series of clues about people living in houses of different colors, with each person having a different nationality, pet, drink, and flower.
The puzzle can be solved using deductive reasoning and a list of logical rules.
Additional details
Some say Einstein created the puzzle as a young man for fun.
Others claim he used it to select the smartest PhD students to supervise.
Some online claims say Lewis Carroll, the author of Alice's Adventures in Wonderland, invented the puzzle.