Given an integer array `nums`, you need to find one continuous subarray that if you only sort this subarray in ascending order, then the whole array will be sorted in ascending order.

Return the shortest such subarray and output its length.

Example 1:

```Input: nums = [2,6,4,8,10,9,15]
Output: 5
Explanation: You need to sort [6, 4, 8, 10, 9] in ascending order to make the whole array sorted in ascending order.
```

Example 2:

```Input: nums = [1,2,3,4]
Output: 0
```

Example 3:

```Input: nums = [1]
Output: 0
```

Constraints:

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

Solution:

``````/**
* @param {number[]} nums
* @return {number}
*/
var findUnsortedSubarray = function(nums) {
if (!nums || nums.length <= 1) return 0;
let len = nums.length;
let l = 0;
let r = len - 1;

// Scan from left to right and find the first element
// which is greater than the next element
for (; l < len; l++) {
if (nums[l] > nums[l + 1]) break;
}
if (l === len) return 0; // sorted already!
// Scan from right to left and find the first element
// which is smaller than the next element
for (; r > 0; r--) {
if (nums[r] < nums[r - 1]) break;
}

// Find the minimum and maximum values in arr[l..r]
let arr = nums.slice(l, r + 1);
let min = Math.min(...arr);
let max = Math.max(...arr);

// Find the first element (if there is any) in arr[0..l]
// which is greater than min
for (let i = 0; i < l; i++) {
if (nums[i] > min) {
l = i;
break;
}
}

// Find the last element (if there is any) in arr[r..n-1]
// which is smaller than max
for (let i = len ; i > r; i--) {
if (nums[i] < max) {
r = i;
break;
}
}

let gap = r - l + 1;
return gap;
};``````