## Problem Statement

Given an array, find the length of the smallest subarray in it which when sorted will sort the whole array.

**Example 1**:

```
Input: [1, 2, 5, 3, 7, 10, 9, 12]
Output: 5
Explanation: We need to sort only the subarray [5, 3, 7, 10, 9] to make the whole array sorted
```

**Example 2**:
```
Input: [1, 3, 2, 0, -1, 7, 10]
Output: 5
Explanation: We need to sort only the subarray [1, 3, 2, 0, -1] to make the whole array sorted
```

**Example 3**:
```
Input: [1, 2, 3]
Output: 0
Explanation: The array is already sorted
```
**Example 4**:
```
Input: [3, 2, 1]
Output: 3
Explanation: The whole array needs to be sorted.
```

**Constraints:**

- 1 <= arr.length <= 104
- -105 <= arr[i] <= 105

## Try it yourself   
Try solving this question here:

```
Input: [1, 2, 5, 3, 7, 10, 9, 12]
Output: 5
Explanation: We need to sort only the subarray [5, 3, 7, 10, 9] to make the whole array sorted
```

**Example 2**:
```
Input: [1, 3, 2, 0, -1, 7, 10]
Output: 5
Explanation: We need to sort only the subarray [1, 3, 2, 0, -1] to make the whole array sorted
```

**Example 3**:
```
Input: [1, 2, 3]
Output: 0
Explanation: The array is already sorted
```
**Example 4**:
```
Input: [3, 2, 1]
Output: 3
Explanation: The whole array needs to be sorted.
```

```
Input: [1, 2, 5, 3, 7, 10, 9, 12]
Output: 5
Explanation: We need to sort only the subarray [5, 3, 7, 10, 9] to make the whole array sorted
```

**Example 2**:
```
Input: [1, 3, 2, 0, -1, 7, 10]
Output: 5
Explanation: We need to sort only the subarray [1, 3, 2, 0, -1] to make the whole array sorted
```

**Example 3**:
```
Input: [1, 2, 3]
Output: 0
Explanation: The array is already sorted
```
**Example 4**:
```
Input: [3, 2, 1]
Output: 3
Explanation: The whole array needs to be sorted.
```

**Constraints:**

- `1 <= arr.length <= 104`
- `-105 <= arr[i] <= 105`