Update complexity comments to show initial and optimal time complexities

Author: RahwaZeslusHaile

Sprint-1/JavaScript/calculateSumAndProduct/calculateSumAndProduct.js

@@ -9,9 +9,9 @@
  *   "product": 30 // 2 * 3 * 5
  * }
  *
- * Time Complexity: O(n)
+ * Initial Time Complexity: O(n) [multiple passes]
  * Space Complexity: O(1)
- * Optimal Time Complexity: O(n)
+ * Optimal Time Complexity: O(n) [single pass]
  *
  * @param {Array<number>} numbers - Numbers to process
  * @returns {Object} Object containing running total and product

Sprint-1/JavaScript/findCommonItems/findCommonItems.js

@@ -1,9 +1,9 @@
 /**
  * Finds common items between two arrays.
  *
- * Time Complexity: O(n + m)
+ * Initial Time Complexity: O(n × m) [filter with includes]
  * Space Complexity: O(n + m)
- * Optimal Time Complexity: O(n + m)
+ * Optimal Time Complexity: O(n + m) [with Set]
  *
  * @param {Array} firstArray - First array to compare
  * @param {Array} secondArray - Second array to compare

Sprint-1/JavaScript/hasPairWithSum/hasPairWithSum.js

@@ -1,9 +1,9 @@
 /**
  * Find if there is a pair of numbers that sum to a given target value.
  *
- * Time Complexity: O(n)
+ * Initial Time Complexity: O(n²) [nested loops]
  * Space Complexity: O(n)
- * Optimal Time Complexity: O(n)
+ * Optimal Time Complexity: O(n) [with Set]
  *
  * @param {Array<number>} numbers - Array of numbers to search through
  * @param {number} target - Target sum to find

Sprint-1/JavaScript/removeDuplicates/removeDuplicates.mjs

@@ -1,9 +1,9 @@
 /**
  * Remove duplicate values from a sequence, preserving the order of the first occurrence of each value.
  *
- * Time Complexity: O(n)
+ * Initial Time Complexity: O(n²) [nested loops]
  * Space Complexity: O(n)
- * Optimal Time Complexity: O(n)
+ * Optimal Time Complexity: O(n) [with Set]
  *
  * @param {Array} inputSequence - Sequence to remove duplicates from
  * @returns {Array} New sequence with duplicates removed