# Single Number

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

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

## Solutions

### 🧠 Cpp

```cpp
class Solution {
public:
    int singleNumber(vector<int>& nums)
    {
        for(int i=0; i < nums.size(); ++i)
        {
            for(int j=0; ; ++j)
                if(nums[i] == nums[j] && i != j)
                    break;
                else if (j == nums.size()-1)
                    return nums[i]; 
        }

        return 0;
    }
};
```