1574. Shortest Subarray to be Removed to Make Array Sorted

Description

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

 

Solutions

Solution: Two Pointers

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

 

JavaScript

/**
 * @param {number[]} arr
 * @return {number}
 */
const findLengthOfShortestSubarray = function (arr) {
  const size = arr.length;
  let right = size - 1;

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

  if (right === 0) return 0;
  let result = right;

  for (let index = 0; index < size; index++) {
    if (arr[index - 1] > arr[index]) break;
    while (arr[index] > arr[right]) right += 1;
    result = Math.min(result, right - index - 1);
  }
  return result;
};