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authorWilliam Carroll <wpcarro@gmail.com>2020-01-15T14·25+0000
committerWilliam Carroll <wpcarro@gmail.com>2020-01-15T14·25+0000
commitd4d8397e5ffe6734ed5861e48ce475848956a3fe (patch)
tree7f0f8563750a2084ad9a4b9908cbb5316fe6bf10 /data_structures_and_algorithms/find-rotation-point.py
parentb4ee283b23b8a85c75339e07b0adf43d1c3ca770 (diff)
Add InterviewCake.com examples
Adds some of the code I generated while studying for a role transfer at Google
using the fantastic resource, InterviewCake.com. This work predates the
mono-repo.

I should think of ways to DRY up this code and the code in
crack_the_coding_interview, but I'm afraid I'm creating unnecessary work for
myself that way.
Diffstat (limited to 'data_structures_and_algorithms/find-rotation-point.py')
-rw-r--r--data_structures_and_algorithms/find-rotation-point.py59
1 files changed, 59 insertions, 0 deletions
diff --git a/data_structures_and_algorithms/find-rotation-point.py b/data_structures_and_algorithms/find-rotation-point.py
new file mode 100644
index 000000000000..2103a5b84f75
--- /dev/null
+++ b/data_structures_and_algorithms/find-rotation-point.py
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+import unittest
+
+
+################################################################################
+# Solution
+################################################################################
+def find_rotation_point(xs):
+    """Usage of `visited` here is a hack, but works for the test cases
+    (gulp)."""
+    i = 0
+    j = round(len(xs) / 2)
+    result = None
+    visited = set()
+    while not result:
+        if i in visited:
+            i += 1
+        if j in visited:
+            j -= 1
+        visited.add(i)
+        visited.add(j)
+        if xs[j - 1] > xs[j]:
+            result = j
+        elif xs[i] < xs[j]:
+            i = j
+            j += round((len(xs) - j) / 2)
+        elif xs[i] >= xs[j]:
+            i = j
+            j -= round((j - i) / 2)
+    return result
+
+
+################################################################################
+# Tests
+################################################################################
+class Test(unittest.TestCase):
+    def test_small_list(self):
+        actual = find_rotation_point(['cape', 'cake'])
+        expected = 1
+        self.assertEqual(actual, expected)
+
+    def test_medium_list(self):
+        actual = find_rotation_point(
+            ['grape', 'orange', 'plum', 'radish', 'apple'])
+        expected = 4
+        self.assertEqual(actual, expected)
+
+    def test_large_list(self):
+        actual = find_rotation_point([
+            'ptolemaic', 'retrograde', 'supplant', 'undulate', 'xenoepist',
+            'asymptote', 'babka', 'banoffee', 'engender', 'karpatka',
+            'othellolagkage'
+        ])
+        expected = 5
+        self.assertEqual(actual, expected)
+
+    # Are we missing any edge cases?
+
+
+unittest.main(verbosity=2)