subarray-product-less-than-k.js

/**
 * Subarray Product Less Than K
 *
 * Your are given an array of positive integers nums.
 *
 * Count and print the number of (contiguous) subarrays where the product of all the elements in the subarray is 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.
 */

/**
 * @param {number[]} nums
 * @param {number} k
 * @return {number}
 */
const numSubarrayProductLessThanK = (nums, k) => {
  let count = 0;
  let product = 1;

  for (let i = 0, j = 0; j < nums.length; j++) {
    product *= nums[j];

    while (i <= j && product >= k) {
      product /= nums[i++];
    }

    count += j - i + 1;
  }

  return count;
};

export { numSubarrayProductLessThanK };