diff --git a/src/my_project/interviews/amazon_high_frequency_23/common_algos/two_sum_round_19.py b/src/my_project/interviews/amazon_high_frequency_23/common_algos/two_sum_round_19.py
new file mode 100644
index 00000000..6c0c6330
--- /dev/null
+++ b/src/my_project/interviews/amazon_high_frequency_23/common_algos/two_sum_round_19.py
@@ -0,0 +1,16 @@
+from typing import List, Union, Collection, Mapping, Optional
+from abc import ABC, abstractmethod
+
+class Solution:
+    def twoSum(self, nums: List[int], target: int) -> List[int]:
+
+        answer = dict()
+
+        for k, v in enumerate(nums):
+
+            if v in answer:
+                return [answer[v], k]
+            else:
+                answer[target - v] = k
+
+        return []
\ No newline at end of file
diff --git a/src/my_project/interviews/amazon_high_frequency_23/common_algos/valid_palindrome_round_19.py b/src/my_project/interviews/amazon_high_frequency_23/common_algos/valid_palindrome_round_19.py
new file mode 100644
index 00000000..1ed43720
--- /dev/null
+++ b/src/my_project/interviews/amazon_high_frequency_23/common_algos/valid_palindrome_round_19.py
@@ -0,0 +1,23 @@
+from typing import List, Union, Collection, Mapping, Optional
+from abc import ABC, abstractmethod
+import re
+
+class Solution:
+    def isPalindrome(self, s: str) -> bool:
+
+        # To lowercase
+        s = s.lower()
+
+        # Remove non-alphanumeric characters
+        s = re.sub(pattern='[^a-zA-Z0-9]', repl='', string=s)
+
+        # Determine if s is palindrome or not
+
+        len_s = len(s)
+
+        for i in range(len_s//2):
+
+            if s[i] != s[len_s - 1 - i]:
+                return False 
+            
+        return True 
\ No newline at end of file
diff --git a/src/my_project/interviews/top_150_questions_round_21/permutations.py b/src/my_project/interviews/top_150_questions_round_21/permutations.py
new file mode 100644
index 00000000..a4632058
--- /dev/null
+++ b/src/my_project/interviews/top_150_questions_round_21/permutations.py
@@ -0,0 +1,21 @@
+from typing import List, Union, Collection, Mapping, Optional
+from abc import ABC, abstractmethod
+
+class Solution:
+    def permute(self, nums: List[int]) -> List[List[int]]:
+
+        final_answer = list()
+
+        def back(answer = list()):
+            if len(answer) == len(nums):
+                final_answer.append(answer)
+                return 
+            
+            for num in nums:
+                if num not in answer:
+                    new_arr = answer + [num]
+                    back(new_arr)
+
+        back()
+
+        return final_answer
\ No newline at end of file
diff --git a/tests/test_150_questions_round_21/test_permutations_round_21.py b/tests/test_150_questions_round_21/test_permutations_round_21.py
new file mode 100644
index 00000000..95569315
--- /dev/null
+++ b/tests/test_150_questions_round_21/test_permutations_round_21.py
@@ -0,0 +1,11 @@
+import unittest
+from src.my_project.interviews.top_150_questions_round_21\
+.permutations import Solution
+
+class PermutationTestCase(unittest.TestCase):
+
+    def test_permutation_1(self):
+        solution = Solution()
+        output = solution.permute(nums = [1,2,3])
+        target = [[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]]
+        self.assertEqual(output, target)
\ No newline at end of file