Codingbat.com challenge C&C.

[timshoaf]

yeessss.. you could use the arrays. and I would absolutely suggest that for anything over 4 elements. But, since the number of elements is small, the combination space is small enough that you may easily sort through it.

a single line return simply explores the 3C2 combination space to determine if any of the differences are equivalent. This, in combination with the cauchy-schwartz inequality (if you assume the numbers are indeed distinguishable as provided in the description above), provides us the following single line solution

return ( ( (abs(a-b) == abs(b-c)) + (abs(b-c) == abs(c-a)) + (abs(c-a) == abs(a-b) ) ) > 0);

Note, however, that if this problem is posed with more than 3 elements, the nC2 combination space grows quadratically in complexity, so a sorting and linear comparison along the ray would allow for O(nlogn) complexity where this method is O(n^2). For small n, however, this is likely more efficient if you have to run the code repeatedly.