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# 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
```

```java
class Solution {
    public int singleNumber(int[] nums) {
        int x = nums[0];
        for (int i = 1; i < nums.length; i++) {
            x = x ^ nums[i];
        }
        return x;
    }
}
```