Find a pair of elements from an array whose sum equals a given number

Question

Given array of n integers and given a number X, find all the unique pairs of elements (a,b), whose summation is equal to X.

The following is my solution, it is O(nLo

Answer 1

https://github.com/clockzhong/findSumPairNumber

I did it under O(m+n) complexity cost for both time and memory space. I suspect that's the best algorithm so far.