Sum of Bit Differences Among All Pairs

Given an integer array of n integers, find sum of bit differences in all pairs that can be formed from array elements. Bit difference of a pair (x, y) is count of different bits at same positions in binary representations of x and y. For example, bit difference for 2 and 7 is 2. Binary representation of 2 is 010 and 7 is 111.

Note: (x, y) and (y, x) should be counted seperately.

Contributed by Berkan Teber