无聊的刷题笔记

Single Number

LeetCode 136

Given a non-empty 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?

Example 1:

Input: [2,2,1]
Output: 1

Example 2:

Input: [4,1,2,1,2]
Output: 4

class Solution(object):
def singleNumber(self, nums):
"""
:type nums: List[int]
:rtype: int
"""
s = set()
for i in nums:
if i in s:
s.remove(i)
else:
s.add(i)
return s.pop()