713. Subarray Product Less Than K

MediumLeetCode

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

How to solve the problem

• Approach: Sliding Window

Code

class Solution:
    def numSubarrayProductLessThanK(self, nums: List[int], k: int) -> int:
        left = 0
        prod = 1
        count = 0
        if k <= 1:
            return 0
        for right, x in enumerate(nums):
            prod *= x
            while prod >= k:
                prod /= nums[left]
                left += 1
            count += right - left + 1
        return count

Complexity

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