Single Number

Problem Statement

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.

Leetcode Link

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.

Code

Python

class Solution:
    def singleNumber(self, nums: List[int]) -> int:
        return reduce(lambda total, el: total ^ el, nums)