79 lines
2.2 KiB
Python
79 lines
2.2 KiB
Python
import unittest
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################################################################################
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# Solution
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################################################################################
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# reverse :: List(a) -> List(a)
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def reverse(node):
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curr = node
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prev = None
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while curr:
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nxt = curr.next
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curr.next = prev
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prev = curr
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curr = nxt
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# Make sure to understand the spec! Debugging takes time. Rewriting takes
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# time.
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return prev
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################################################################################
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# Tests
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################################################################################
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class Test(unittest.TestCase):
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class LinkedListNode(object):
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def __init__(self, value, next=None):
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self.value = value
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self.next = next
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def get_values(self):
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node = self
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values = []
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while node is not None:
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values.append(node.value)
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node = node.next
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return values
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def test_short_linked_list(self):
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second = Test.LinkedListNode(2)
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first = Test.LinkedListNode(1, second)
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result = reverse(first)
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self.assertIsNotNone(result)
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actual = result.get_values()
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expected = [2, 1]
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self.assertEqual(actual, expected)
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def test_long_linked_list(self):
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sixth = Test.LinkedListNode(6)
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fifth = Test.LinkedListNode(5, sixth)
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fourth = Test.LinkedListNode(4, fifth)
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third = Test.LinkedListNode(3, fourth)
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second = Test.LinkedListNode(2, third)
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first = Test.LinkedListNode(1, second)
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result = reverse(first)
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self.assertIsNotNone(result)
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actual = result.get_values()
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expected = [6, 5, 4, 3, 2, 1]
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self.assertEqual(actual, expected)
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def test_one_element_linked_list(self):
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first = Test.LinkedListNode(1)
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result = reverse(first)
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self.assertIsNotNone(result)
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actual = result.get_values()
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expected = [1]
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self.assertEqual(actual, expected)
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def test_empty_linked_list(self):
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result = reverse(None)
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self.assertIsNone(result)
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unittest.main(verbosity=2)
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