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

# Single Number

Given a **non-empty** array of integers, every element appears\_twice\_except for one. Find that single one.

## Example

**Example 1:**

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

Output:
 1
```

**Example 2:**

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

Output:
 4
```

## Note

使用异或

## Code

```java
class Solution {
    public int singleNumber(int[] nums) {
        int res = 0;
        for(int i = 0; i < nums.length; i++)
            res ^= nums[i];
        return res;
    }
}
```