1679 Shortest Subarray To Be Removed To Make Array Sorted

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:
    def findLengthOfShortestSubarray(self, arr: List[int]) -> int:
        right = len(arr) - 1
        while right > 0 and arr[right] >= arr[right - 1]:
            right -= 1

        ans = right
        left = 0
        while left < right and (left == 0 or arr[left - 1] <= arr[left]):
            # find next valid number after arr[left]
            while right < len(arr) and arr[left] > arr[right]:
                right += 1
            # save length of removed subarray
            ans = min(ans, right - left - 1)
            left += 1
        return ans