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Count Subarrays With Score Less Than K

Hard

The score of an list is defined as the product of its sum and its length.

  • For example, the score of [1, 2, 3, 4, 5] is (1 + 2 + 3 + 4 + 5) * 5 = 75 .

Given a positive integer array nums and an integer k , produce the number of non-empty subarrays of nums whose score is strictly less than k .

A sublist is a contiguous sequence of elements within an array.

Example 1

Input: nums = [2,1,4,3,5], k = 10

Output: 6

Explanation: The 6 subarrays having scores less than 10 are:

  • [2] with score 2 * 1 = 2.

  • [1] with score 1 * 1 = 1.

  • [4] with score 4 * 1 = 4.

  • [3] with score 3 * 1 = 3.

  • [5] with score 5 * 1 = 5.

  • [2,1] with score (2 + 1) * 2 = 6.

Note that subarrays such as [1,4] and [4,3,5] are not considered because their scores are 10 and 36 respectively, while we need scores strictly less than 10.

Example 2

Input: nums = [1,1,1], k = 5

Output: 5

Explanation: Every subarray except [1,1,1] has a score less than 5.

[1,1,1] has a score (1 + 1 + 1) * 3 = 9, which is greater than 5.

Thus, there are 5 subarrays having scores less than 5.

Constraints

  • 1 <= nums.length <= 10^5
  • 1 <= nums[i] <= 10^5
  • 1 <= k <= 10^15

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