Single Number

题目描述

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?

解题方法

记录每个bit的出现次数

用一个array或者hashmap记录每个bit 1的出现次数，如果是奇数次就是single number里的

XOR

Solution

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

        return result

Reference