713. Subarray Product Less Than K

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

Solution

subarray-product-less-than-k.py

class Solution:
    def numSubarrayProductLessThanK(self, nums: List[int], k: int) -> int:
        n = len(nums)
        res = 0
        left = right = 0
        curr = 1

        while right < n:
            curr *= nums[right]

            while left <= right and curr >= k:
                curr //= nums[left]
                left += 1

            res += right - left + 1
            right += 1

        return res

subarray-product-less-than-k.cpp

class Solution {
public:
    int numSubarrayProductLessThanK(vector<int>& nums, int k) {
        int c = 1, res = 0;

        for (int i = 0,j = 0; j < nums.size(); j++){
            c *= nums[j];
            while (i <= j && c >= k)
                c /= nums[i++];
            res += (j - i + 1);
        }

        return res;
    }
};