diff --git a/src/my_project/interviews/top_150_questions_round_20/happy_number.py b/src/my_project/interviews/top_150_questions_round_20/happy_number.py
new file mode 100644
index 00000000..72982656
--- /dev/null
+++ b/src/my_project/interviews/top_150_questions_round_20/happy_number.py
@@ -0,0 +1,18 @@
+from typing import List, Union, Collection, Mapping, Optional
+from abc import ABC, abstractmethod
+
+class Solution(object):
+    def isHappy(self, n):
+
+        set_answer = set()
+
+        while n != 1:
+
+            if n not in set_answer:
+                set_answer.add(n)
+            else: 
+                return False 
+            
+            n = sum([int(c)**2 for c in str(n)])
+
+        return True
\ No newline at end of file
diff --git a/tests/test_150_questions_round_20/test_happy_number_round_20.py b/tests/test_150_questions_round_20/test_happy_number_round_20.py
new file mode 100644
index 00000000..f1dc1135
--- /dev/null
+++ b/tests/test_150_questions_round_20/test_happy_number_round_20.py
@@ -0,0 +1,15 @@
+import unittest
+from src.my_project.interviews.top_150_questions_round_20\
+.happy_number import Solution
+
+class HappyNumberTestCase(unittest.TestCase):
+
+    def test_is_happy_number(self):
+        solution = Solution()
+        output = solution.isHappy(n=19)
+        self.assertTrue(output)
+
+    def test_is_no_happy_number(self):
+        solution = Solution()
+        output = solution.isHappy(n=2)
+        self.assertFalse(output)
\ No newline at end of file