刷题

1.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?

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