LeetCode - Single Number

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?

Solution : Using XOR logic

#!/bin/python
def singleNumber(self, a):
        uniq = 0
        for k in a:
            uniq ^= k
        return uniq
        """
        :type nums: List[int]
        :rtype: int
        """