713. Subarray Product Less Than K

Problem

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 * 10^4

• 1 <= nums[i] <= 1000

• 0 <= k <= 10^6

Solution (Java)

class Solution {
    public int numSubarrayProductLessThanK(int[] nums, int k) {
        int p = 1;
        int j = 0;
        int ans = 0;
        for (int i = 0; i < nums.length; i++) {
            p = p * nums[i];
            while (p >= k && j < i) {
                p = p / nums[j];
                j++;
            }
            ans += p < k ? i - j + 1 : 0;
        }
        return ans;
    }
}

Explain:

nope.

Complexity:

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