remove duplicates

Author: ebrahimbeiati

Sprint-1/JavaScript/removeDuplicates/removeDuplicates.mjs

@@ -1,36 +1,27 @@
 /**
  * Remove duplicate values from a sequence, preserving the order of the first occurrence of each value.
  *
- * Time Complexity:
- * Space Complexity:
- * Optimal Time Complexity:
+ * Time Complexity: O(n²)
+ * Space Complexity: O(n)
+ * Optimal Time Complexity: O(n)
+ * Explanation: The function checks each element against all previously seen elements to determine,
+ * if it is a duplicate, resulting in a time complexity of O(n²) in the worst case.
+ * The space complexity is O(n) because we are storing unique items in a new array.
+ *  The optimal time complexity can be achieved by using a Set to track seen items,
+ * which allows for O(1) average time complexity for lookups, resulting in an overall time complexity of O(n).
+ * Refactor: Using Set allows to constant-time membership checks, which significantly reduces the time complexity from O(n²) to O(n).
  *
  * @param {Array} inputSequence - Sequence to remove duplicates from
  * @returns {Array} New sequence with duplicates removed
  */
 export function removeDuplicates(inputSequence) {
+  const seen = new Set();
   const uniqueItems = [];
-
-  for (
-    let currentIndex = 0;
-    currentIndex < inputSequence.length;
-    currentIndex++
-  ) {
-    let isDuplicate = false;
-    for (
-      let compareIndex = 0;
-      compareIndex < uniqueItems.length;
-      compareIndex++
-    ) {
-      if (inputSequence[currentIndex] === uniqueItems[compareIndex]) {
-        isDuplicate = true;
-        break;
-      }
-    }
-    if (!isDuplicate) {
-      uniqueItems.push(inputSequence[currentIndex]);
+  for (const item of inputSequence) {
+    if (!seen.has(item)) {
+      seen.add(item);
+      uniqueItems.push(item);
     }
   }
-
   return uniqueItems;
 }