Given an array of numbers which contains all the numbers in pairs expect one element. We have to find that unique element.

For example in the array [7,3,8,1,3,4,7,1,8] 4 is the unique element and all the remaining elements occur in pairs.

This is actually a specific case of more generic problem discussed in the my previous post.

http://comproguide.blogspot.in/2013/06/finding-element-occurring-odd-number-of.html

please refer to the above post for complete solution.