solution.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.

 

# 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
 

# Constraints:

# 1 <= nums.length <= 3 * 104
# -3 * 104 <= nums[i] <= 3 * 104
# Each element in the array appears twice except for one element which appears only once.

from typing import List

class Solution:
    def singleNumber(self, nums: List[int]) -> int:
        # XOR ^
        # a ^ a = 0 
	    # a ^ 0 = a 

        unique_element = 0
        
        for num in nums:
            unique_element ^= num
        
        return unique_element