find common items

Author: ebrahimbeiati

Sprint-1/JavaScript/findCommonItems/findCommonItems.js

@@ -1,14 +1,26 @@
 /**
  * Finds common items between two arrays.
  *
- * Time Complexity:
- * Space Complexity:
- * Optimal Time Complexity:
- *
+ * Time Complexity: O(n * m)
+ * Space Complexity: O(k)---> where k is the number of common items
+ * Optimal Time Complexity: O(n + m)
+ * Explanation: The function uses the filter method to iterate through each item in the first array and
+ * checks if it exists in the second array using the includes method.
+ * This results in a time complexity of O(n * m) because for each item in the first array,
+ * we are checking against all items in the second array.
+ *  The space complexity is O(k) because we are creating a new array to store the common items,
+ *  where k is the number of common items found.
  * @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))),
-];
+export const findCommonItems = (firstArray, secondArray) => {
+  const lookup = new Set(secondArray);
+  const result = new Set();
+  for (const item of firstArray) {
+    if (lookup.has(item)) {
+      result.add(item);
+    }
+  }
+  return [...result];
+};