713. Subarray Product Less Than K¶

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713. Subarray Product Less Than K

Medium

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¶

class Solution {
    public int numSubarrayProductLessThanK(int[] nums, int k) {
        int n = nums.length;
        int left = 0;
        long current_prod = 1, total = 0;
        for (int right = 0; right < n; right++) {
            current_prod *= nums[right];
            while (left < right && current_prod >= k) current_prod /= nums[left++];
            if (current_prod < k) total += (right - left + 1);
        }
        return (int)total;
    }
}

Complexity Analysis¶

• Time Complexity: O(?)
• Space Complexity: O(?)

Approach¶

Detailed explanation of the approach will be added here