Einstein’s Puzzle

This challenging logic puzzle is often attributed to Albert Einstein, along with the claim that 98 percent of the population cannot solve it. It is presented below as a playable HTML5 game. The conditions are listed below, and you can click and drag the elements within the frame to see if you can solve the puzzle.

There are five different color houses, occupied by people of five different nationalities, who each have a different pet and drink a different beverage. Strangely, they have all made the poor decision to smoke cigarettes, and each has a different brand.

The Rules

• the Briton occupies the red house
• the Spaniard has a dog
• the person in the green house drinks coffee
• the Ukrainian drinks tea
• the green house is directly to the left of the white house
• the person who smokes Old Gold has a snail for a pet
• the person in the yellow house smokes Kools
• the person living in the center house prefers milk
• the Norwegian occupies the first house
• the person who smokes Chesterfields lives directly next to the person who owns a fox
• the person who owns a horse lives next to the person who smokes Kools
• the person who smokes Lucky Strike drinks orange juice
• the Japanese person smokes Parliaments
• the Norwegian lives next to the blue house
• the Chesterfield smoker has a neighbor who drinks water

The question is: Who owns the fish?

The animation above will not prevent you from making wrong moves or tell you if you put the fish in the right place. If you need a hint, start reading the Explanation below. When you think you have solved it, click See Answer below to see if you’re right.

Explanation

You can use the grid however you like; I chose to put the houses in the first row, followed by nationalities, beverages, cigarettes and pets.

Start with the most definite items. The Norwegian occupies the first house, so we can place that one immediately. Next, the Norwegian lives next to the blue house, so the blue house must be in the second position. The person in the center house prefers milk, so we can place milk in the center.

For the next step, we have to combine two rules. We know the green house must be to the immediate left of the white house, and the green house occupant drinks coffee. So green and white can only fit in the fourth and fifth positions.

Now we can place the Briton in the red house in the third position, which means the yellow house must be in the first position. Based on the rules, we can then place Kools in the first column and the horse in the second column.

With nothing else definite to go on, we should look for limited options, i.e. combinations of elements that could only go in one of two positions. The Lucky Strike and orange juice combination is one of these: it can only go in position 2 or 5. We can try tentatively placing it in position 2 and see what happens. Since the Ukrainian drinks tea, the Ukrainian must go in column 5. But then we would have to place water in column 1 and we are unable to fulfill the rule that the Chesterfield smoker has a neighbor who drinks water. What this test showed us is that Lucky Strike and orange juice cannot go in position 2 and therefore they must go in position 5.

Now the Ukrainian drinking tea must go in position 2, leaving only position 1 for water, and we know that Chesterfield must go next to water in position 2.

Next, the Japanese person smokes Parliaments, and this can only happen in position 4. That leaves only position 5 for the Spaniard, who we know owns a dog.

There is now only position 2 left for Old Gold, where the snail must also go. Since we know the Chesterfield smoker has a fox for a neighbor, the fox goes in position 1. This leaves only one slot left for the fish and gives us our answer.