Whose Fish?

The Puzzle

There are five houses in a row in different colors. In each house lives a person with a different nationality. The five owners drink a different drink, smoke a different brand of cigar and keep a different pet, one of which is a Walleye Pike. The question is-- who owns the fish? Hints:

1. The Brit lives in the red house.
2. The Swede keeps dogs as pets.
3. The Dane drinks tea.
4. The green house is on the left of the white house.
5. The green house owner drinks coffee.
6. The person who smokes Pall Malls keeps birds.
7. The owner of the yellow house smokes Dunhills.
8. The man living in the house right in the center drinks milk.
9. The man who smokes Blends lives next to the one who keeps cats.
10. The Norwegian lives in the first house.
11. The man who keeps horses lives next to the one who smokes Dunhills.
12. The owner who smokes Bluemasters drinks beer.
13. The German smokes Princes.
14. The Norwegian lives next to the blue house.
15. The man who smokes Blends has a neighbor who drinks water.

There are no tricks, pure logic will get you the correct answer. And yes, there is enough information to arrive at the one and only correct answer.

My way...

Turns out you can solve this puzzle almost the same way you do Sudoku. Start with this, the possibilities for each property of each house (more printable version here):

We'll figure this out by eliminating possibilities one at a time until we're left with the right answer.

To do this, you just step through the hints one at a time, striking out the options eliminated by that step. If you get to the end of the hints and you haven't gotten the answer yet, you loop back to hint #1 and keep going.

For example, the first clue, "The Brit lives in the red house" doesn't tell us anything at this point, so we go to the next question.

Turns out the first usable clue here is #8, "The man living in the house right in the center drinks milk". With that clue, we can eliminate every other drink in the middle house, and eliminate milk from every other house. Now it looks like this (you might have to look closely to see the lines through the drinks):

If you print out the hints, you can cross out hint #8 since we used all the information it had, and that reminds you to skip it the next time around.

The next one that's usable is #10, telling us that the Norwegian is in house #1. Again, we strike the other nationalities in house #1, and strike Norwegian from the boxes on the other houses.

One of the tricks to remember comes from clues like #4, The green house is on the left of the white house. We can't do much with that early, but once we know that the blue house is house #2, that clue tells us that house #1 can't be the green house or the white house. In fact, #3 can't be the white house either, since the one on its left is blue. We cross all those off.

Clue #5 then tells us that The green house owner drinks coffee, so all the ones that we know *aren't* green definitely *aren't* coffee drinkers either, so we can cross those off too.

In fact, when you get to clues like #2, "The Swede keeps dogs as pets", you can also think in your mind: "not Swede, not dogs". Then, go through each house, and if you've already crossed off Swede, you can also cross off dogs.

If you keep iterating, you can end up crossing off all the options in a cell except one, e.g. Dane in house #2. Then you cross Dane off of all the other houses, and keep going. You should get the answer in about 15 minutes.

Here's where I end up:

Answer: German, house 4, fish.