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# Bit Manipulation: Lonely Integer

# Bit Manipulation: Lonely Integer

Check out the resources on the page's right side to learn more about bit manipulation. The video tutorial is by Gayle Laakmann McDowell, author of the best-selling interview book Cracking the Coding Interview.

Consider an array of integers where all but one of the integers occur in pairs. In other words, every element occurs exactly twice except for one unique element. Find the unique element.

For example, given the array , you would return .

**Function Description**

Complete the *findLonely* function in the editor below. It should return the unique integer in .

findLonely has the following parameter(s):

*arr*: an array of integers

**Input Format**

The first line contains a single integer, , denoting the number of integers in .

The second line contains space-separated integers, each an element, .

**Constraints**

- It is guaranteed that is an odd number.
- , where .

**Output Format**

Print the unique number in on a new line.

**Sample Input 0**

```
1
1
```

**Sample Output 0**

```
1
```

**Explanation 0**

The array only contains a single , so we print as our answer.

**Sample Input 1**

```
3
1 1 2
```

**Sample Output 1**

```
2
```

**Explanation 1**

We have two 's and one . We print , because that's the only unique element in the array.

**Sample Input 2**

```
5
0 0 1 2 1
```

**Sample Output 2**

```
2
```

**Explanation 2**

We have two 's, two 's, and one . We print , because that's the only unique element in the array.