Shortest subarray to be removed to make array sorted

We will use two pointers to find the longest subarray that is sorted. The answer will be the length of the array minus the length of the longest subarray.

class Solution:
    def findLengthOfShortestSubarray(self, arr: List[int]) -> int:
        arr = [0] + arr + [math.inf]

        l, r = 0, len(arr)-1
        shortest = math.inf
        while l < len(arr)-2 and arr[l] <= arr[l+1]:
            l += 1

        while l >= 0:
            while r-1 > l and arr[r-1] >= arr[l] and arr[r] >= arr[r-1]:
                r -= 1
            shortest = min(shortest, r-l-1)
            l -= 1

        return shortest

Time complexity: O(n)
Space complexity: O(1)