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# Single Number

[Single Number](https://leetcode.com/problems/single-number/)

{% embed url="<https://leetcode.com/problems/single-number/>" %}

Given a **non-empty** array of integers, every element appears *twice* except for one. Find that single one.

**Note:**

Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory?

**Example 1:**

```
Input: [2,2,1]
Output: 1
```

**Example 2:**

```
Input: [4,1,2,1,2]
Output: 4
```