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

# Single Number

题目：

Given 2\*n + 1 numbers, every numbers occurs twice except one, find it.

分析：

异或，相同数异或会抵消,两两抵消。a^a=0 0^a = a

解法：

```
 public int singleNumber(int[] A) {
        // Write your code here
        int ret = 0;
        for(int i = 0; i< A.length; i++){
            ret^=A[i];
        }
        return ret;
    }
```