019f8fd211
git-subtree-dir: users/wpcarro git-subtree-mainline:464bbcb15cgit-subtree-split:24f5a642afChange-Id: I6105b3762b79126b3488359c95978cadb3efa789
114 lines
2.8 KiB
Python
114 lines
2.8 KiB
Python
import unittest
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################################################################################
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# InterviewCake's solution
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################################################################################
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def cycle_len(xs, i):
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"""
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Returns the length of a cycle that contains no duplicate items.
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"""
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result = 1
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checkpt = i
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current = xs[checkpt - 1]
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while current != checkpt:
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current = xs[current - 1]
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result += 1
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return result
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def theirs(xs):
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"""
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This is InterviewCake's solution.
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"""
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i = xs[-1]
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for _ in range(len(xs) - 1):
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i = xs[i - 1]
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cycle_length = cycle_len(xs, i)
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p0 = xs[-1]
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p1 = xs[-1]
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for _ in range(cycle_length):
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p1 = xs[p1 - 1]
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while p0 != p1:
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p0 = xs[p0 - 1]
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p1 = xs[p1 - 1]
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print(p0, p1)
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return p0
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################################################################################
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# My solution
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################################################################################
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def mine(xs):
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"""
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This is the solution that I came up with, which differs from InterviewCake's
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solution.
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"""
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i = xs[-1]
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offset = 1 if len(xs) % 2 == 0 else 2
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for _ in range(len(xs) - offset):
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i = xs[i - 1]
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return i
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use_mine = True
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find_duplicate = mine if use_mine else theirs
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# Tests
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class Test(unittest.TestCase):
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def test_just_the_repeated_number(self):
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# len(xs) even
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actual = find_duplicate([1, 1])
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expected = 1
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self.assertEqual(actual, expected)
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def test_short_list(self):
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# len(xs) even
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actual = find_duplicate([1, 2, 3, 2])
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expected = 2
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self.assertEqual(actual, expected)
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def test_medium_list(self):
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# len(xs) even
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actual = find_duplicate([1, 2, 5, 5, 5, 5])
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expected = 5
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self.assertEqual(actual, expected)
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def test_long_list(self):
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# len(xs) odd
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actual = find_duplicate([4, 1, 4, 8, 3, 2, 7, 6, 5])
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expected = 4
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self.assertEqual(actual, expected)
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############################################################################
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# Additional examples from InterviewCake.com
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############################################################################
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def test_example_a(self):
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# len(xs) even
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actual = find_duplicate([3, 4, 2, 3, 1, 5])
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expected = 3
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self.assertTrue(actual, expected)
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def test_example_b(self):
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# len(xs) even
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actual = find_duplicate([3, 1, 2, 2])
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expected = 2
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self.assertEqual(actual, expected)
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def test_example_c(self):
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# len(xs) odd BUT multiple duplicates
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actual = find_duplicate([4, 3, 1, 1, 4])
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self.assertTrue(actual in {1, 4})
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unittest.main(verbosity=2)
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