LeetCode如何查出只出现一次的数

1

题目描述

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知识点

class Solution:    def singleNumber(self, nums: List[int]) -> int:        countnum=dict()        for i in nums:            if i in countnum:                countnum[i]=countnum[i]+1            else:                countnum[i]=1        for e,v in countnum.items():            if v == 1:                return e

class Solution:    def singleNumber(self, nums: List[int]) -> int:        nums.sort()         return list(set(nums[::2]) - set(nums[1::2]))[0]

class Solution:    def singleNumber(self, nums: List[int]) -> int:        res = 0        for i in nums:            res ^= i        return res