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?

//位運算 亦或
    public int singleNumber(int[] nums) {

        int result = nums[0];

        for (int i = 1; i < nums.length; i++) {
            result = result^nums[i];
        }
        return result;
    }