Tried Solving Code Evals Jolly Jumper problem by using Arithmetic Progressions (Gaus)
Which will not work since their can be specific duplicates that would add up to the same sum
For example: n=4, [1,2,1,5] sum: 1+1+4 = 6   expected: (3*(4))/2 = 6

Will change it, so that is keeps track of the differences.
Implemented solution for CodeEval's Jolly Jumpers challenge
https://www.codeeval.com/open_challenges/43/