diff --git a/src/my_project/interviews/interview_amazon/round_4/algo_1.py b/src/my_project/interviews/interview_amazon/round_4/algo_1.py
new file mode 100644
index 00000000..c1da49a2
--- /dev/null
+++ b/src/my_project/interviews/interview_amazon/round_4/algo_1.py
@@ -0,0 +1,59 @@
+from typing import List 
+
+class Solution:
+
+    def solution_1(self, names: List[str]):
+        dic_answer = dict()
+
+        for n in names:
+            
+            if n not in dic_answer:
+                dic_answer[n] = 1
+            else: 
+                dic_answer[n] += 1
+
+        names.sort(key=lambda x: dic_answer[x], reverse=True)
+
+        return names[0], dic_answer[names[0]]
+    
+    def solution_2(self, names: List[str]):
+
+        names.sort(key=lambda x: len(x), reverse=True)
+
+        return len(names[0]), names[0]
+    
+    def solution_3(self, nums: List[str]):
+
+        return len([n for n in nums if n % 7 == 0])
+    
+
+    def solution_4(self, input_file):
+
+        with open(input_file, 'r') as infile, \
+             open('odd_numbers.txt', 'w') as odd_nums, \
+             open('even_numbers.txt', 'w') as even_nums:
+            
+            for line in infile:
+                if not line:
+                    continue
+                try:
+                    num = int(line)
+                    if num % 2 == 0:
+                        even_nums.write(f'{num}\n')
+                    else: 
+                        odd_nums.write(f'{num}\n')
+                except ValueError:
+                    continue
+
+        
+    
+
+solution = Solution()
+
+print(solution.solution_1(names=['mariana','luis','mariana']))
+
+print(solution.solution_2(names=['mariana','luis','leonardo']))
+
+print(solution.solution_3(nums=[7,14,5,6,9]))
+
+solution.solution_4(input_file='numbers.txt')
\ No newline at end of file
diff --git a/src/my_project/interviews/interview_amazon/round_4/even_numbers.txt b/src/my_project/interviews/interview_amazon/round_4/even_numbers.txt
new file mode 100644
index 00000000..e5b350fa
--- /dev/null
+++ b/src/my_project/interviews/interview_amazon/round_4/even_numbers.txt
@@ -0,0 +1,3 @@
+4
+8
+10
diff --git a/src/my_project/interviews/interview_amazon/round_4/numbers.txt b/src/my_project/interviews/interview_amazon/round_4/numbers.txt
new file mode 100644
index 00000000..e38a5bb5
--- /dev/null
+++ b/src/my_project/interviews/interview_amazon/round_4/numbers.txt
@@ -0,0 +1,6 @@
+1
+3
+4
+8
+10
+7
\ No newline at end of file
diff --git a/src/my_project/interviews/interview_amazon/round_4/odd_numbers.txt b/src/my_project/interviews/interview_amazon/round_4/odd_numbers.txt
new file mode 100644
index 00000000..47ae665d
--- /dev/null
+++ b/src/my_project/interviews/interview_amazon/round_4/odd_numbers.txt
@@ -0,0 +1,3 @@
+1
+3
+7
diff --git a/src/my_project/interviews/interview_amazon/round_5/valid_palindrome.py b/src/my_project/interviews/interview_amazon/round_5/valid_palindrome.py
new file mode 100644
index 00000000..c32d4bf3
--- /dev/null
+++ b/src/my_project/interviews/interview_amazon/round_5/valid_palindrome.py
@@ -0,0 +1,20 @@
+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)
+
+        # find palindrome
+        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_17/longest_common_prefix.py b/src/my_project/interviews/top_150_questions_round_17/longest_common_prefix.py
new file mode 100644
index 00000000..4d5cf93d
--- /dev/null
+++ b/src/my_project/interviews/top_150_questions_round_17/longest_common_prefix.py
@@ -0,0 +1,21 @@
+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 ''
+        else:
+            min_strs, max_strs = min(strs), max(strs)
+            count = 0
+
+            len_min_strs = len(min_strs)
+
+            for i in range(len_min_strs):
+                if min_strs[i] != max_strs[i]:
+                    break 
+                else:
+                    count += 1
+
+            return min_strs[:count]
diff --git a/tests/test_150_questions_round_17/test_longest_common_prefix_round_17.py b/tests/test_150_questions_round_17/test_longest_common_prefix_round_17.py
new file mode 100644
index 00000000..24ed788e
--- /dev/null
+++ b/tests/test_150_questions_round_17/test_longest_common_prefix_round_17.py
@@ -0,0 +1,23 @@
+import unittest
+from src.my_project.interviews.top_150_questions_round_17\
+.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)
\ No newline at end of file