713. Subarray Product Less Than K

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713. Subarray Product Less Than K

Description

Difficulty: Medium

Related Topics: Array, Sliding Window

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:

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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:

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Input: nums = [1,2,3], k = 0
Output: 0

Constraints:

  • 1 <= nums.length <= 3 * 104
  • 1 <= nums[i] <= 1000
  • 0 <= k <= 106

Hints/Notes

  • Sliding window
  • How to calculate the subArray

Solution

Language: C++

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class Solution {
public:
    int numSubarrayProductLessThanK(vector<int>& nums, int k) {
        int left = 0, right = 0, res = 0;
        long prod = 1;
        while (right < nums.size()) {
            prod *= nums[right];
            if (prod >= k) {
                while (left <= right && prod >= k) {
                    prod /= nums[left++];
                }
            }
            res += right - left + 1;
            right++;
        }
        return res;
    }
};