feature(C02_P05): add recursive solution to sum lists with improved t…

…ests

chapter_02/p05_sum_lists.py

@@ -1,3 +1,5 @@
+import pytest
+
 from chapter_02.linked_list import LinkedList
 
 
@@ -23,34 +25,40 @@ def sum_lists(ll_a, ll_b):
     return ll
 
 
-# this solution does not pass tests
-# def sum_lists_followup(ll_a, ll_b):
-#     # Pad the shorter list with zeros
-#     if len(ll_a) < len(ll_b):
-#         for i in range(len(ll_b) - len(ll_a)):
-#             ll_a.add_to_beginning(0)
-#     else:
-#         for i in range(len(ll_a) - len(ll_b)):
-#             ll_b.add_to_beginning(0)
-#
-#     # Find sum
-#     n1, n2 = ll_a.head, ll_b.head
-#     result = 0
-#     while n1 and n2:
-#         result = (result * 10) + n1.value + n2.value
-#         n1 = n1.next
-#         n2 = n2.next
-#
-#     # Create new linked list
-#     return NumericLinkedList([int(i) for i in str(result)])
+def sum_lists_recursive(ll_a, ll_b) -> "NumericLinkedList":
+    def sum_lists_helper(ll1_head, ll2_head, remainder, summed_list):
+        if ll1_head is None and ll2_head is None:
+            if remainder != 0:
+                summed_list.add(remainder)
+            return summed_list
+        elif ll1_head is None:
+            result = ll2_head.value + remainder
+            summed_list.add(result % 10)
+            return sum_lists_helper(ll1_head, ll2_head.next, result // 10, summed_list)
+        elif ll2_head is None:
+            result = ll1_head.value + remainder
+            summed_list.add(result % 10)
+            return sum_lists_helper(ll1_head.next, ll2_head, result // 10, summed_list)
+        else:
+            result = ll1_head.value + ll2_head.value + remainder
+            summed_list.add(result % 10)
+            return sum_lists_helper(
+                ll1_head.next, ll2_head.next, result // 10, summed_list
+            )
+
+    return sum_lists_helper(ll_a.head, ll_b.head, 0, NumericLinkedList())
 
 
 class NumericLinkedList(LinkedList):
-    @classmethod
-    def generate_from_integer(cls, integer):
-        integer_parts = [int(c) for c in str(integer)]
-        integer_parts.reverse()
-        return cls(integer_parts)
+    def __init__(self, values=None):
+        """handle integer as input"""
+        if isinstance(values, int):
+            values = [int(c) for c in str(values)]
+            values.reverse()
+        elif isinstance(values, list):
+            values = values.copy()
+
+        super().__init__(values)
 
     def numeric_value(self):
         number = 0
@@ -59,47 +67,47 @@ def numeric_value(self):
         return number
 
 
-test_cases = (
-    # all values can either be list of integer or integers
-    # a, b, expected_sum
-    ([7, 1, 6], [5, 9, 2], [2, 1, 9]),
-    (0, 0, 0),
-    ([], [], 0),
-    ([3, 2, 1], [3, 2, 1], [6, 4, 2]),
-    (123, 123, 246),
-    (123, 1, 124),
-    (1, 123, 124),
-)
+def test_numeric_linked_list():
+    ll = NumericLinkedList(321)
+    assert ll.numeric_value() == 321
+    assert ll.values() == [1, 2, 3]
 
-testable_functions = (
-    sum_lists,
-    # sum_lists_followup
-)
 
+testable_functions = (sum_lists, sum_lists_recursive)
 
-def test_numeric_linked_list():
-    ll = NumericLinkedList.generate_from_integer(321)
-    assert ll.numeric_value() == 321
+
+@pytest.fixture(params=testable_functions)
+def linked_list_summing_function(request):
+    return request.param
+
+
+test_cases = (
+    # inputs can either be list of integer or integers
+    # a, b, expected_sum
+    pytest.param([1], [2], [3], id="single_digit"),
+    pytest.param([0], [0], [0], id="single_digit_zero"),
+    pytest.param([], [], [], id="empty"),
+    pytest.param([7, 1, 6], [5, 9, 2], [2, 1, 9], id="3-digit equal length A"),
+    pytest.param([3, 2, 1], [3, 2, 1], [6, 4, 2], id="3-digit equal length B"),
+    pytest.param(123, 1, [4, 2, 1], id="3-digit and single digit"),
+    pytest.param([9, 9, 9], [1], [0, 0, 0, 1], id="carry end"),
+    pytest.param([9, 9, 9], [9, 9, 9], [8, 9, 9, 1], id="multiple carry"),
+)
 
 
-def test_linked_list_addition():
-    for f in testable_functions:
-        for a, b, expected in test_cases:
-            print(f"{f.__name__}: {a}, {b}, {expected}")
-            if isinstance(a, int):
-                ll_a = NumericLinkedList.generate_from_integer(a)
-            else:
-                ll_a = NumericLinkedList(a.copy())
+@pytest.mark.parametrize("a, b, expected", test_cases)
+def test_linked_list_addition(linked_list_summing_function, a, b, expected):
+    ll_a = NumericLinkedList(a)
+    ll_b = NumericLinkedList(b)
+    ll_result = linked_list_summing_function(ll_a, ll_b)
+    assert ll_result.values() == expected
+    assert (
+        ll_a.numeric_value() + ll_b.numeric_value()
+        == NumericLinkedList(expected).numeric_value()
+    )
 
-            if isinstance(b, int):
-                ll_b = NumericLinkedList.generate_from_integer(b)
-            else:
-                ll_b = NumericLinkedList(b.copy())
-            result = f(ll_a, ll_b)
-            if isinstance(expected, int):
-                assert result.numeric_value() == expected
-            else:
-                assert result.values() == expected
+    ll_result_reverse = linked_list_summing_function(ll_b, ll_a)
+    assert ll_result_reverse.values() == expected
 
 
 def example():
@@ -108,8 +116,8 @@ def example():
     print(ll_a)
     print(ll_b)
     print(sum_lists(ll_a, ll_b))
-    # print(sum_lists_followup(ll_a, ll_b))
 
 
 if __name__ == "__main__":
     example()
+    pytest.main(args=[__file__])

tox.ini

@@ -10,3 +10,4 @@ ignore = C0102,C0111,C0203,C0301,C0302,C0325,C0330,C0412,C0413,C901,E0101,E0202,
 [flake8]
 max-line-length = 88
 extend-ignore = E203,E800,VNE001,VNE002
+pytest-parametrize-names-type = csv