Add problem 66 - Plus One

Author: anirudhology

problems/math/plus_one.py

@@ -0,0 +1,16 @@
+from typing import List
+
+
+class PlusOne:
+    @staticmethod
+    def plusOne(digits: List[int]) -> List[int]:
+        n = len(digits)
+        for i in range(n - 1, -1, -1):
+            if digits[i] < 9:
+                digits[i] += 1
+                return digits
+            digits[i] = 0
+
+        output = [0] * (n + 1)
+        output[0] = 1
+        return output

tests/math/plus_one_test.py

@@ -0,0 +1,25 @@
+import unittest
+
+from problems.math.plus_one import PlusOne
+
+
+class TestPlusOne(unittest.TestCase):
+
+    def setUp(self):
+        self.plus_one = PlusOne()
+
+    def test_plus_one_no_carry_over(self):
+        self.assertEqual(self.plus_one.plusOne([1, 2, 3]), [1, 2, 4])
+
+    def test_plus_one_with_carry_over_in_middle(self):
+        self.assertEqual(self.plus_one.plusOne([1, 2, 9]), [1, 3, 0])
+
+    def test_plus_one_with_all_nines(self):
+        self.assertEqual(self.plus_one.plusOne([9, 9, 9]), [1, 0, 0, 0])
+
+    def test_plus_one_empty_array(self):
+        self.assertEqual(self.plus_one.plusOne([]), [1])
+
+
+if __name__ == '__main__':
+    unittest.main()