Given an array of integers numsand 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

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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

这次还是双指针。只是别人的代码优化了一下；

Runtime: 9 ms, faster than 22.60% of Java online submissions for Subarray Product Less Than K.

Memory Usage: 50.3 MB, less than 22.13% of Java online submissions for Subarray Product Less Than K.