Leetcode: Single Number @Python

Use bitwise XOR. For each bit, odd number of appearance of 0/1 will still be 0/1, even number of appearance of 0/1 will be 0. And since for any number x, 0^x=x, use 0 as the initial value for iteration.

class Solution:
    # @param A, a list of integer
    # @return an integer
    def singleNumber(self, A):
        rst=0
        for i in A:
            rst^=i
        return rst