adding longest common prefix algo

src/my_project/interviews/top_150_questions_round_12/longest_common_prefix.py

@@ -0,0 +1,19 @@
+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
+
+            for i in range(len(min_strs)):
+                if min_strs[i] != max_strs[i]:
+                    break
+                else: 
+                    count += 1
+
+            return min_strs[:count]

tests/test_150_questions_round_12/test_longest_common_prefix_round_12.py

@@ -0,0 +1,23 @@
+import unittest
+from src.my_project.interviews.top_150_questions_round_12\
+.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)