給定一個非空整數陣列，除了某個元素只出現一次以外，其餘每個元素均出現了三次。找出那個只出現了一次的元素。

說明：

你的演算法應該具有線性時間複雜度。 你可以不使用額外空間來實現嗎？

示例 1:

輸入: [2,2,3,2]
輸出: 3

示例 2:

輸入: [0,1,0,1,0,1,99]
輸出: 99

class Solution(object):
    def singleNumber(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        res = [0 for _ in range(32)]
        for i in range(32):
            for ele in nums:
                if ele & (2 ** i) == pow(2, i):
                    res[i] += 1
        res = [ele % 3 for ele in res]
        result = 0
        if res[-1] == 0:
            for ind, ele in enumerate(res):
                if ele == 1:
                    result |= 2 ** ind
            return result
        else:
            for ind, ele in enumerate(res[:-1]):
                if ele == 0:
                    result |= 2 ** ind
            return -(result + 1)