# Challenge 7: Find First Unique Integer in an Array

"Unique" means the number does not repeat and appears only once in the whole array. Implement the optimized solution in C# and see if it runs correctly.

## We'll cover the following

## Problem statement

Implement a function, `findFirstUnique(int[] arr, int size)`

, which takes an array and its size as input and returns the first unique integer in the array. The function returns `-1`

if no unique number is found.

### Input

This is an array of integers and its size

### Output

This is the first unique element in the array

### Sample input

```
[2,3,9,2,3,6]
```

### Sample output

```
9
```

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