add subarray_product_less_than_k

Author: akgmage

Sliding Window/subarray_product_less_than_k,js

@@ -0,0 +1,50 @@
+/**
+     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.
+
+    The provided code defines a Java class Solution with a method numSubarrayProductLessThanK that counts the number 
+    of subarrays in an input array nums whose product is less than a given threshold k. It uses a sliding window 
+    approach to efficiently compute this count.
+
+    Time Complexity:
+
+    The code iterates through the nums array once, using two pointers (startWindow and endWindow) to define the 
+    sliding window. This results in a time complexity of O(N), where N is the length of the input array nums.
+    Space Complexity:
+
+    The code uses a constant amount of additional space to store integer variables (startWindow, product, and count). 
+    Therefore, the space complexity is O(1), which means it is independent of the size of the input array.
+ */
+class Solution {
+  numSubarrayProductLessThanK(nums, k) {
+    let startWindow = 0; // The left end of the sliding window
+    let product = 1; // Initialize product to 1 to accumulate the product
+    let count = 0; // Count of subarrays with a product less than k
+
+    // Iterate through the array using a sliding window approach
+    for (let endWindow = 0; endWindow < nums.length; endWindow++) {
+      // Multiply the current element to the product
+      product *= nums[endWindow];
+
+      // Shrink the window by moving the start pointer as long as the product is greater than or equal to k
+      while (startWindow <= endWindow && product >= k) {
+        // Divide the product by the element at the start of the window
+        product /= nums[startWindow];
+        // Move the start of the window to the right
+        startWindow++;
+      }
+
+      // Update the count with the number of valid subarrays within the current window
+      count += endWindow - startWindow + 1;
+    }
+
+    // Return the count, which represents the number of subarrays with a product less than k
+    return count;
+  }
+}
+
+// Example usage
+const solution = new Solution();
+const result = solution.numSubarrayProductLessThanK([10, 5, 2, 6], 100);
+console.log(result); // Output: 8