diff --git a/src/my_project/interviews/amazon_high_frequency_23/round_2/valid_palindrom_round_3.py b/src/my_project/interviews/amazon_high_frequency_23/round_2/valid_palindrom_round_3.py
new file mode 100644
index 00000000..0f3740de
--- /dev/null
+++ b/src/my_project/interviews/amazon_high_frequency_23/round_2/valid_palindrom_round_3.py
@@ -0,0 +1,21 @@
+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)
+
+        # Check if it 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
diff --git a/src/my_project/interviews/top_150_questions_round_21/longest_common_prefix.py b/src/my_project/interviews/top_150_questions_round_21/longest_common_prefix.py
new file mode 100644
index 00000000..509c29d1
--- /dev/null
+++ b/src/my_project/interviews/top_150_questions_round_21/longest_common_prefix.py
@@ -0,0 +1,20 @@
+from typing import List, Union, Collection, Mapping, Optional
+from abc import ABC, abstractmethod
+
+class Solution:
+    def longestCommonPrefix(self, strs: List[str]) -> str:
+
+        if not strs:
+            return ''
+        
+        min_strs, max_strs = min(strs), max(strs)
+        count = 0
+
+        for i in range(len(min_strs)):
+
+            if min_strs[i] == max_strs[i]:
+                count +=1
+            else: 
+                break
+
+        return min_strs[:count]
diff --git a/tests/test_150_questions_round_21/test_longest_common_prefix_round_21.py b/tests/test_150_questions_round_21/test_longest_common_prefix_round_21.py
new file mode 100644
index 00000000..2e7bffb9
--- /dev/null
+++ b/tests/test_150_questions_round_21/test_longest_common_prefix_round_21.py
@@ -0,0 +1,23 @@
+import unittest
+from src.my_project.interviews.top_150_questions_round_21\
+.longest_common_prefix import Solution
+
+class LongestCommonPrefixTestCase(unittest.TestCase):
+
+    def test_longest_common_prefix(self):
+        solution = Solution()
+        output = solution.longestCommonPrefix(strs=["flower","flow","flight"])
+        target = 'fl'
+        self.assertEqual(target, output)
+
+    def test_longest_no_common_prefix(self):
+        solution = Solution()
+        output = solution.longestCommonPrefix(strs=["dog","racecar","car"])
+        target = ''
+        self.assertEqual(target, output)
+
+    def test_longest_common_prefix_null_list(self):
+        solution = Solution()
+        output = solution.longestCommonPrefix(strs=[])
+        target = ''
+        self.assertEqual(target, output)