# Leetcode - Single Number Solution

Given a **non-empty** array of integers `nums`

, every element appears *twice* except for one. Find that single one.

**Follow up:** Could you implement a solution with a linear runtime complexity and without using extra memory?

**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.

## Solution in python

```
class Solution:
def singleNumber(self, nums: List[int]) -> int:
return sum(set(nums))*2-sum(nums)
```