Problem · Array

Count the Number of Incremovable Subarrays II

MediumThe D. E. Shaw GroupOA

You are given a 0-indexed array of positive integers nums.

A subarray of nums is called incremovable if nums becomes strictly increasing on removing the subarray. For example, the subarray [3, 4] is an incremovable subarray of [5, 3, 4, 6, 7] because removing this subarray changes the array [5, 3, 4, 6, 7] to [5, 6, 7], which is strictly increasing.

Return the total number of incremovable subarrays of nums.

Note that an empty array is considered strictly increasing.

A subarray is a contiguous non-empty sequence of elements within an array.

Examples
01 · Example 1
nums = [1,2,3,4]
return = 10

The 10 incremovable subarrays are: [1], [2], [3], [4], [1,2], [2,3], [3,4], [1,2,3], [2,3,4], and [1,2,3,4], because on removing any one of these subarrays nums becomes strictly increasing. Note that you cannot select an empty subarray.

02 · Example 2
nums = [6,5,7,8]
return = 7

The 7 incremovable subarrays are: [5], [6], [5,7], [6,5], [5,7,8], [6,5,7], and [6,5,7,8]. It can be shown that there are only 7 incremovable subarrays in nums.

03 · Example 3
nums = [8,7,6,6]
return = 3

The 3 incremovable subarrays are: [8,7,6], [7,6,6], and [8,7,6,6]. Note that [8,7] is not an incremovable subarray because after removing [8,7] nums becomes [6,6], which is sorted in ascending order but not strictly increasing.

Constraints
  • 1 <= nums.length <= 10^5
  • 1 <= nums[i] <= 10^9
More The D. E. Shaw Group problems
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public int countIncremovableSubarrays(int[] nums) {
  // write your code here (You might want to refer to LC2972:)
}
nums[1,2,3,4]
expected10
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