diff --git a/Sprint-1/JavaScript/calculateSumAndProduct/calculateSumAndProduct.js b/Sprint-1/JavaScript/calculateSumAndProduct/calculateSumAndProduct.js
index ce738c3..a2686c0 100644
--- a/Sprint-1/JavaScript/calculateSumAndProduct/calculateSumAndProduct.js
+++ b/Sprint-1/JavaScript/calculateSumAndProduct/calculateSumAndProduct.js
@@ -18,17 +18,24 @@
  */
 export function calculateSumAndProduct(numbers) {
   let sum = 0;
-  for (const num of numbers) {
-    sum += num;
-  }
-
   let product = 1;
   for (const num of numbers) {
+    sum += num;
     product *= num;
   }
-
   return {
     sum: sum,
     product: product,
   };
 }
+// Time Complexity: O(n)
+// The original implementation also had O(n) time complexity,
+// but it iterated through the array twice (approximately 2n operations).
+// The refactored version calculates both the sum and product in one loop,
+// so it only traverses the array once (approximately n iterations).
+//
+// Space Complexity: O(1)
+// We only store two variables regardless of the size of the input.
+// Optimal Time Complexity: O(n)
+// We must iterate through every element at least once
+// to calculate both the sum and the product.
diff --git a/Sprint-1/JavaScript/findCommonItems/findCommonItems.js b/Sprint-1/JavaScript/findCommonItems/findCommonItems.js
index 5619ae5..61814f4 100644
--- a/Sprint-1/JavaScript/findCommonItems/findCommonItems.js
+++ b/Sprint-1/JavaScript/findCommonItems/findCommonItems.js
@@ -9,6 +9,33 @@
  * @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 findCommonItems2 = (firstArray, secondArray) => [
+//   ...new Set(firstArray.filter((item) => secondArray.includes(item))), //O(N*M)
+// ];
+export const findCommonItems = (firstArray, secondArray) => {
+  const secondSet = new Set(secondArray); //O(M)
+  const commonSet = new Set();
+
+  for (const item of firstArray) {
+    //O(N)
+    if (secondSet.has(item)) {
+      commonSet.add(item);
+    }
+  }
+
+  return [...commonSet]; //O(K)
+};
+// Time Complexity: O(n + m)
+// We create a Set from secondArray and loop through firstArray once.
+
+// Original Time Complexity: O(n * m)
+// includes() may search all of secondArray for every item in firstArray.
+
+// Space Complexity: O(m + n)
+// We store secondArray in a Set and up to n common items.
+
+// Original Space Complexity: O(n)
+// filter() and Set create temporary collections of up to n items.
+
+// Optimal Time Complexity: O(n + m)
+// We need to inspect both arrays to find all common items.
diff --git a/Sprint-1/JavaScript/hasPairWithSum/hasPairWithSum.js b/Sprint-1/JavaScript/hasPairWithSum/hasPairWithSum.js
index dd2901f..e38d9f3 100644
--- a/Sprint-1/JavaScript/hasPairWithSum/hasPairWithSum.js
+++ b/Sprint-1/JavaScript/hasPairWithSum/hasPairWithSum.js
@@ -9,13 +9,38 @@
  * @param {number} target - Target sum to find
  * @returns {boolean} True if pair exists, false otherwise
  */
+// export function hasPairWithSum2(numbers, target) {
+//   for (let i = 0; i < numbers.length; i++) {
+//     for (let j = i + 1; j < numbers.length; j++) {
+//       if (numbers[i] + numbers[j] === target) {
+//         return true;
+//       }
+//     }
+//   }
+//   return false;
+// }
+// Time Complexity: O(N^2)
+// Space Complexity: O(1)
+// Optimal Time Complexity: O(N)
+
 export function hasPairWithSum(numbers, target) {
-  for (let i = 0; i < numbers.length; i++) {
-    for (let j = i + 1; j < numbers.length; j++) {
-      if (numbers[i] + numbers[j] === target) {
-        return true;
-      }
-    }
+  const seen = new Set();
+  for (const num of numbers) {
+    const needed = target - num;
+    if (seen.has(needed)) return true;
+
+    seen.add(num);
   }
+
   return false;
 }
+// Original Time Complexity: O(n^2)
+//two nested loop compare each number with remaining numbers
+
+// Time Complexity: O(n)
+// we iterate through the arr once and Set.has() for O(1) lookup
+
+// Space Complexity: O(n)
+// We may store up to n numbers in the Set.
+// Optimal Time Complexity: O(n)
+//we might need to inspect every number at least once.
diff --git a/Sprint-1/JavaScript/removeDuplicates/removeDuplicates.mjs b/Sprint-1/JavaScript/removeDuplicates/removeDuplicates.mjs
index dc5f771..96ebf7d 100644
--- a/Sprint-1/JavaScript/removeDuplicates/removeDuplicates.mjs
+++ b/Sprint-1/JavaScript/removeDuplicates/removeDuplicates.mjs
@@ -8,29 +8,46 @@
  * @param {Array} inputSequence - Sequence to remove duplicates from
  * @returns {Array} New sequence with duplicates removed
  */
+// export function removeDuplicates(inputSequence) {
+//   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]);
+//     }
+//   }
+
+//   return uniqueItems;
+// }
+
 export function removeDuplicates(inputSequence) {
-  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]);
-    }
-  }
-
-  return uniqueItems;
+
+  return [...new Set(inputSequence)];  //O(N+N)
 }
+
+// Original Time Complexity: O(n * k), worst case O(n^2)
+// For each item, the code may scan all uniqueItems to check for duplicates.
+
+// Time Complexity: O(n)
+// Creating the Set processes each item once, and spreading it back to an array is also O(n).
+
+// Space Complexity: O(n)
+// The Set and returned array can store up to n unique items.
+
+// Optimal Time Complexity: O(n)
+// We must inspect every element at least once to remove duplicates.
\ No newline at end of file
diff --git a/Sprint-1/Python/calculate_sum_and_product/calculate_sum_and_product.py b/Sprint-1/Python/calculate_sum_and_product/calculate_sum_and_product.py
index cfd5cfd..2da0cd3 100644
--- a/Sprint-1/Python/calculate_sum_and_product/calculate_sum_and_product.py
+++ b/Sprint-1/Python/calculate_sum_and_product/calculate_sum_and_product.py
@@ -1,31 +1,39 @@
 from typing import Dict, List
 
+# def calculate_sum_and_product(input_numbers: List[int]) -> Dict[str, int]:
+#     """
+#     Calculate the sum and product of integers in a list.
 
-def calculate_sum_and_product(input_numbers: List[int]) -> Dict[str, int]:
-    """
-    Calculate the sum and product of integers in a list.
+#     Note: the sum is every number added together
+#     and the product is every number multiplied together
+#     so for example: [2, 3, 5] would return
+#     {
+#         "sum": 10, // 2 + 3 + 5
+#         "product": 30 // 2 * 3 * 5
+#     }
+#     Time Complexity:
+#     Space Complexity:
+#     Optimal time complexity:
+#     """
+#     # Edge case: empty list
+#     if not input_numbers:
+#         return {"sum": 0, "product": 1}
+
+#     sum = 0
+#     for current_number in input_numbers:
+#         sum += current_number
 
-    Note: the sum is every number added together
-    and the product is every number multiplied together
-    so for example: [2, 3, 5] would return
-    {
-        "sum": 10, // 2 + 3 + 5
-        "product": 30 // 2 * 3 * 5
-    }
-    Time Complexity:
-    Space Complexity:
-    Optimal time complexity:
-    """
-    # Edge case: empty list
-    if not input_numbers:
-        return {"sum": 0, "product": 1}
+#     product = 1
+#     for current_number in input_numbers:
+#         product *= current_number
 
-    sum = 0
-    for current_number in input_numbers:
-        sum += current_number
 
-    product = 1
-    for current_number in input_numbers:
-        product *= current_number
+#     return {"sum": sum, "product": product}
+def calculate_sum_and_product(input_numbers: List[int]) -> Dict[str, int]:
+    total: int = 0
+    product: int = 1
+    for num in input_numbers:
+        total += num
+        product *= num
 
-    return {"sum": sum, "product": product}
+    return {"sum": total, "product": product}
diff --git a/Sprint-1/Python/find_common_items/find_common_items.py b/Sprint-1/Python/find_common_items/find_common_items.py
index 478e2ef..b59c198 100644
--- a/Sprint-1/Python/find_common_items/find_common_items.py
+++ b/Sprint-1/Python/find_common_items/find_common_items.py
@@ -3,19 +3,31 @@
 ItemType = TypeVar("ItemType")
 
 
+# def find_common_items(
+#     first_sequence: Sequence[ItemType], second_sequence: Sequence[ItemType]
+# ) -> List[ItemType]:
+#     """
+#     Find common items between two arrays.
+
+#     Time Complexity:
+#     Space Complexity:
+#     Optimal time complexity:
+#     """
+#     common_items: List[ItemType] = []
+#     for i in first_sequence:
+#         for j in second_sequence:
+#             if i == j and i not in common_items:
+#                 common_items.append(i)
+#     return common_items
+
+
 def find_common_items(
     first_sequence: Sequence[ItemType], second_sequence: Sequence[ItemType]
 ) -> List[ItemType]:
-    """
-    Find common items between two arrays.
-
-    Time Complexity:
-    Space Complexity:
-    Optimal time complexity:
-    """
-    common_items: List[ItemType] = []
-    for i in first_sequence:
-        for j in second_sequence:
-            if i == j and i not in common_items:
-                common_items.append(i)
-    return common_items
+    first_set = set(first_sequence)
+    second_set = set(second_sequence)
+
+    common = first_set.intersection(second_set)
+    # common = first_set & second_set
+
+    return list(common)
diff --git a/Sprint-1/Python/has_pair_with_sum/has_pair_with_sum.py b/Sprint-1/Python/has_pair_with_sum/has_pair_with_sum.py
index fe2da51..d0bcbdf 100644
--- a/Sprint-1/Python/has_pair_with_sum/has_pair_with_sum.py
+++ b/Sprint-1/Python/has_pair_with_sum/has_pair_with_sum.py
@@ -3,16 +3,27 @@
 Number = TypeVar("Number", int, float)
 
 
+# def has_pair_with_sum(numbers: List[Number], target_sum: Number) -> bool:
+#     """
+#     Find if there is a pair of numbers that sum to a target value.
+
+#     Time Complexity:
+#     Space Complexity:
+#     Optimal time complexity:
+#     """
+#     for i in range(len(numbers)):
+#         for j in range(i + 1, len(numbers)):
+#             if numbers[i] + numbers[j] == target_sum:
+#                 return True
+#     return False
+
 def has_pair_with_sum(numbers: List[Number], target_sum: Number) -> bool:
-    """
-    Find if there is a pair of numbers that sum to a target value.
+    seen  = set()
+    for num in numbers:
+        needed = target_sum - num
+        if needed in seen:
+            return True
+
+        seen.add(num)
 
-    Time Complexity:
-    Space Complexity:
-    Optimal time complexity:
-    """
-    for i in range(len(numbers)):
-        for j in range(i + 1, len(numbers)):
-            if numbers[i] + numbers[j] == target_sum:
-                return True
     return False
diff --git a/Sprint-1/Python/remove_duplicates/remove_duplicates.py b/Sprint-1/Python/remove_duplicates/remove_duplicates.py
index c9fdbe8..67f9b02 100644
--- a/Sprint-1/Python/remove_duplicates/remove_duplicates.py
+++ b/Sprint-1/Python/remove_duplicates/remove_duplicates.py
@@ -3,23 +3,34 @@
 ItemType = TypeVar("ItemType")
 
 
-def remove_duplicates(values: Sequence[ItemType]) -> List[ItemType]:
-    """
-    Remove duplicate values from a sequence, preserving the order of the first occurrence of each value.
-
-    Time complexity:
-    Space complexity:
-    Optimal time complexity:
-    """
-    unique_items = []
-
-    for value in values:
-        is_duplicate = False
-        for existing in unique_items:
-            if value == existing:
-                is_duplicate = True
-                break
-        if not is_duplicate:
-            unique_items.append(value)
-
-    return unique_items
+# def remove_duplicates(values: Sequence[ItemType]) -> List[ItemType]:
+#     """
+#     Remove duplicate values from a sequence, preserving the order of the first occurrence of each value.
+
+#     Time complexity:
+#     Space complexity:
+#     Optimal time complexity:
+#     """
+#     unique_items = []
+
+#     for value in values:
+#         is_duplicate = False
+#         for existing in unique_items:
+#             if value == existing:
+#                 is_duplicate = True
+#                 break
+#         if not is_duplicate:
+#             unique_items.append(value)
+
+#     return unique_items
+
+def remove_duplicates(values):
+    seen = set()
+    result = []
+
+    for item in values:
+        if item not in seen:
+            seen.add(item)
+            result.append(item)
+
+    return result
\ No newline at end of file