[Leet Code] Single Number

Leet code: https://leetcode.com/problems/single-number/

Problem:

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.

Example 1:

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

Example 2:

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

Example 3:

Input: nums = [1]
Output: 1

Solution:

class Solution(object):
    def singleNumber(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        answers = []
        for i in nums:
            if i in answers:
                answers.pop(answers.index(i))
            else:
                answers.append(i)
                
        return answers[0]