Refactor findCommonItems function to improve time and space complexity, and update documentation

Author: mervereis

Sprint-1/JavaScript/findCommonItems/findCommonItems.js

@@ -1,40 +1,17 @@
 /**
  * Finds common items between two arrays.
  *
- * Time Complexity: O(n * m)
- * Space Complexity: O(n)
- * Optimal Time Complexity: O(n + m)
+ * Time Complexity: O(n + m)
+ * Space Complexity: O(n + m)
  *
  * @param {Array} firstArray - First array to compare
  * @param {Array} secondArray - Second array to compare
  * @returns {Array} Array containing unique common items
  */
 
-export const findCommonItems = (firstArray, secondArray) => [
-  ...new Set(firstArray.filter((item) => secondArray.includes(item))),
-];
-
-// Time complexity is O(n * m) because for each item in the first array,
-// includes() may search through the entire second array.
-
-// Space complexity is O(n) because filter() creates a new array
-// and Set stores unique common items.
-
-// Optimal time complexity is O(n + m) because using Sets
-// allows us to check for common items more efficiently.
 export function findCommonItems(firstArray, secondArray) {
+  const firstSet = new Set(firstArray);
   const secondSet = new Set(secondArray);
-  const commonItems = new Set();
 
-  for (const item of firstArray) {
-    if (secondSet.has(item)) {
-      commonItems.add(item);
-    }
-  }
-
-  return [...commonItems];
+  return [...firstSet.intersection(secondSet)];
 }
-
-// Time complexity: O(n + m)
-// Space complexity: O(n + m)
-// Optimal time complexity: O(n + m)