public int oneNumberOccuringOddTimes(int arr[]){
        int r = 0;
        for(int i=0; i < arr.length; i++){
            r = r^arr[i];
        }
        return r;
    }
http://www.geeksforgeeks.org/find-the-number-occurring-odd-number-of-times/
http://www.geeksforgeeks.org/find-two-non-repeating-elements-in-an-array-of-repeating-elements/
src/com/interview/bits/NumberOccuringOddTimes.java