Day 1: Single Number.py

# Day 1: Single Number

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

"""
Example 1:

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


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