> For the complete documentation index, see [llms.txt](https://nuoxu2016.gitbook.io/algorithms/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://nuoxu2016.gitbook.io/algorithms/bit-operation.md).

# Bit Operation

## 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
```

由于数字在计算机是以二进制存储的，每位上都是0或1，如果我们把两个相同的数字异或，0与0 '异或' 是0，1与1 '异或' 也是0，那么我们会得到0

```cpp
class Solution{
public:
    int bitwise(vector<int>& nums){
        int res = 0;
        for(int num: nums){
         res ^= num
        }
        return res;
    }
}
```