[一起来刷leetcode吧][30]--No.136 Single Number

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这是leetcode的第136题--Single Number

  题目

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?

  思路 如果直接用O(n²)会超时，想到用位运算异或XOR(^)就很简单了，几行代码   

show me the code

class Solution(object):
    def singleNumber(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        num = 0
        for i in nums:
            num ^= i
        return num