Today I have done leetcode's November LeetCoding Challenge with cpp.

November LeetCoding Challenge 15

Description

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

Solution

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

    int left = 0;
    while(left + 1 < len && arr[left] <= arr[left + 1]) left += 1;
    if(left == len - 1) return 0;

    int right = len - 1;
    while(right > left && arr[right - 1] <= arr[right]) right -= 1;

    int answer = min(len - left - 1, right);
    for(int i = 0, j = right; i <= left && j < len;) {
      if(arr[i] <= arr[j]) {
        answer = min(answer, j - i - 1);
        i += 1;
      } else {
        j += 1;
      }
    }
    return answer;
  }
};