leetcode 136. Single Number

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?

解法：

使用xor

class Solution(object):
    def singleNumber(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        """        
        # 3,4,5,3,4,5
        # 3^3 = 0
        # 4^4 = 0
        # 5^5 = 0
        # 0^0 = 0
        # 0^0 = 0
        x = nums[0]
        for i in range(1, len(nums)):
            x ^= nums[i]
        return x
        """
        return reduce(lambda x,y: x^y, nums, 0)
        

语法

reduce() 函数语法：

reduce(function, iterable[, initializer])

参数

• function -- 函数，有两个参数
• iterable -- 可迭代对象
• initializer -- 可选，初始参数