Computing the colors of the Olympic flag

Question

Let's say you are helping setting up the Olympics on an alien planet. You are in charge of making the Olympic flag. The Olympic flag would have 6 colors. The flags of every country on the planet must have one of the six colors on the Olympic flag. You already know the colors on a flag. How would you compute the colors on the Olympic flag? The flag colors are contained in an array of arrays.

Answer 1

Assuming the number of colors is reasonably limited (e.g., if there are 12 colors, there are 924 combinations of 6 of them), I'd use brute force.

Answer 2

My solution: I would create a hash table where key=color, value = integer. Next, I would iterate the countries' flags. for each color I would apply hash(color)++. The colors on the olympic flag are the top 6 colors after sorting the hash table by its values (Where values are are sorted from largest to lowest)