From 7c81c14a2540fabf38b6cb474d64849b8a7ffd67 Mon Sep 17 00:00:00 2001
From: Simran Shrestha <simranstha045@gmail.com>
Date: Sat, 19 Oct 2024 11:57:28 +0545
Subject: [PATCH] Implement Gray Code and Unit Tests

---
 algorithms/bit/__init__.py  |  3 ++-
 algorithms/bit/gray_code.py | 25 +++++++++++++++++++++++++
 tests/test_bit.py           | 24 +++++++++++++++++++++++-
 3 files changed, 50 insertions(+), 2 deletions(-)
 create mode 100644 algorithms/bit/gray_code.py

diff --git a/algorithms/bit/__init__.py b/algorithms/bit/__init__.py
index fa31d7ed8..e0e6213af 100644
--- a/algorithms/bit/__init__.py
+++ b/algorithms/bit/__init__.py
@@ -16,4 +16,5 @@
 from .count_flips_to_convert import *
 from .flip_bit_longest_sequence import *
 from .binary_gap import *
-from .bytes_int_conversion import *
\ No newline at end of file
+from .bytes_int_conversion import *
+from .gray_code import *
\ No newline at end of file
diff --git a/algorithms/bit/gray_code.py b/algorithms/bit/gray_code.py
new file mode 100644
index 000000000..40698806b
--- /dev/null
+++ b/algorithms/bit/gray_code.py
@@ -0,0 +1,25 @@
+"""
+Gray Code Generator
+
+Gray code is a binary numeral system where two successive values differ by only one bit. This function generates a sequence of n-bit Gray codes, where n is the number of bits.
+"""
+
+
+def gray_code(n):
+    """
+    Generate the sequence of n-bit Gray code.
+
+    :param n: Number of bits for the Gray code
+    :return: List of Gray code sequence in decimal representation
+    """
+    if n == 0:
+        return [0]
+
+    # Recursive step: generate (n-1)-bit Gray code
+    previous_gray = gray_code(n - 1)
+
+    # Mirror the previous Gray code
+    new_gray = [(1 << (n - 1)) | i for i in reversed(previous_gray)]
+
+    # Concatenate the old and new mirrored Gray code
+    return previous_gray + new_gray
diff --git a/tests/test_bit.py b/tests/test_bit.py
index c494a9762..7a3aba596 100644
--- a/tests/test_bit.py
+++ b/tests/test_bit.py
@@ -18,7 +18,8 @@
     has_alternative_bit, has_alternative_bit_fast,
     insert_one_bit, insert_mult_bits,
     remove_bit,
-    binary_gap
+    binary_gap,
+    gray_code
 )
 
 import unittest
@@ -270,5 +271,26 @@ def test_binary_gap(self):
         self.assertEqual(4, binary_gap(145))
 
 
+class TestGrayCode(unittest.TestCase):
+    """Unit tests for the Gray Code generator."""
+
+    def test_0_bit_gray_code(self):
+        self.assertEqual(gray_code(0), [0])
+
+    def test_1_bit_gray_code(self):
+        self.assertEqual(gray_code(1), [0, 1])
+
+    def test_2_bit_gray_code(self):
+        self.assertEqual(gray_code(2), [0, 1, 3, 2])
+
+    def test_3_bit_gray_code(self):
+        self.assertEqual(gray_code(3), [0, 1, 3, 2, 6, 7, 5, 4])
+
+    def test_4_bit_gray_code(self):
+        self.assertEqual(gray_code(4), [
+            0, 1, 3, 2, 6, 7, 5, 4, 12, 13, 15, 14, 10, 11, 9, 8
+        ])
+
+
 if __name__ == '__main__':
     unittest.main()