16-single-number.py

# Given a non-empty array of integers nums, every element appears twice except for one. 
# Find that single one.

# You must implement a solution with a linear runtime complexity and use only constant extra space.

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