#+ANKI_DECK: study_deck_02
* TODO 0136. Single Number :easy:
:PROPERTIES:
:NEETCODE: [[file:../../roadmap.org::*0136. Single Number][0136. Single Number]]
:END:

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 * 10^{4}~

 - ~-3 * 10^{4} <= nums[i] <= 3 * 10^{4}~

 - Each element in the array appears twice except for one element which appears only once.

** TODO Approach
Write your approach here.

** TODO Python
#+begin_src python :lc-problem 136 :lc-lang python3
class Solution:
    def singleNumber(self, nums: List[int]) -> int:
#+end_src

** TODO C++
#+begin_src cpp :lc-problem 136
class Solution {
public:
    int singleNumber(vector<int>& nums) {
        
    }
};
#+end_src