Given an array of integers, every element appearstwiceexcept for one. Find that single one.
本题利用XOR的特性， X^0 = X, X^X = 0, 并且XOR满足交换律。
1 class Solution(object): 2def singleNumber(self, nums): 3 """ 4 :type nums: List[int] 5 :rtype: int 6 """ 7 s = 0 8 for x in nums: 9 s= s^x10 11 return s
single number II/III可以用位操作。用Hash table也可以通过OJ
class Solution(object):def singleNumber(self, nums):""":type nums: List[int]:rtype: int"""dict = {}for i in range(len(nums)):if nums[i] not in dict:dict[nums[i]] = 1else:dict[nums[i]] += 1for word in dict:if dict[word] == 1:return word
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