713. Subarray Product Less Than K

Medium
Array
Binary Search
Sliding Window
Prefix Sum

Description

Given an array of integers nums and an integer k, return the number of contiguous subarrays where the product of all the elements in the subarray is strictly less than k.

 

Example 1:

Input: nums = [10,5,2,6], k = 100
Output: 8
Explanation: The 8 subarrays that have product less than 100 are:
[10], [5], [2], [6], [10, 5], [5, 2], [2, 6], [5, 2, 6]
Note that [10, 5, 2] is not included as the product of 100 is not strictly less than k.

Example 2:

Input: nums = [1,2,3], k = 0
Output: 0

 

Constraints:

  • 1 <= nums.length <= 3 * 104
  • 1 <= nums[i] <= 1000
  • 0 <= k <= 106

Hints

Hint 1
For each j, let opt(j) be the smallest i so that nums[i] * nums[i+1] * ... * nums[j] is less than k. opt is an increasing function.

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