1574. Shortest Subarray to be Removed to Make Array Sorted

Given an integer array arr, remove a subarray (can be empty) from arr such that the remaining elements in arr are non-decreasing.

Return the length of the shortest subarray to remove.

A subarray is a contiguous subsequence of the array.

Example 1:

Input: arr = [1,2,3,10,4,2,3,5]
Output: 3
Explanation: The shortest subarray we can remove is [10,4,2] of length 3. The remaining elements after that will be [1,2,3,3,5] which are sorted.
Another correct solution is to remove the subarray [3,10,4].
Example 2:

Input: arr = [5,4,3,2,1]
Output: 4
Explanation: Since the array is strictly decreasing, we can only keep a single element. Therefore we need to remove a subarray of length 4, either [5,4,3,2] or [4,3,2,1].
Example 3:

Input: arr = [1,2,3]
Output: 0
Explanation: The array is already non-decreasing. We do not need to remove any elements.

Constraints:

1 <= arr.length <= 105
0 <= arr[i] <= 109

class Solution {
public:
int findLengthOfShortestSubarray(vector<int>& arr) {
int right = arr.size() - 1;

while (right > 0 && arr[right] >= arr[right - 1]) {
right--;
}

int ans = right;
int left = 0;

while (left < right && (left == 0 || arr[left - 1] <= arr[left])) {

while (right < arr.size() && arr[left] > arr[right]) {
right++;
}
ans = min(ans, right - left - 1);
left++;
}
return ans;
}
};