This problem was asked by Google.
Given a set of distinct positive integers, find the largest subset such that every pair of elements in the subset (i, j) satisfies either i % j = 0 or j % i = 0.
For example, given the set [3, 5, 10, 20, 21], you should return [5, 10, 20]. Given [1, 3, 6, 24], return [1, 3, 6, 24].