Given an array of integers, every element appears twice except for one. Find that single one.

Note:
Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory?

    public int singleNumber(int[] A) {
    	int result = A[0];
    	for (int i = 1; i < A.length; i++) {
    		result = result ^ A[i];
    	}
    	return result;
    }