leetcode#136. Single Number

Description

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?

Code

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

实话说一开始并没有想到位操作，是看答案看到的，遗憾，以后记住了。

def singleNumber3(self, nums):
    return 2*sum(set(nums))-sum(nums)

看到的另一个有趣的答案，利用集合的性质来解决的。不过多亏了python语言的强大，支持这种操作。对于学C出身的我来说，根本就没往这个方向想过，因为实现太麻烦了。