【leetcode】136. 只出现一次的数字（python）位运算（异或运算）

class Solution:
    def singleNumber(self, nums):
        return reduce(lambda x, y: x ^ y, nums)

import collections
class Solution:
    def singleNumber(self, nums):
        dic = collections.Counter(nums)
        for num,cnt in dic.items():
            if cnt == 1:
                return num
        return 0

异或运算，详细请看官方题解