subtree(users/wpcarro): docking briefcase at '24f5a642'

git-subtree-dir: users/wpcarro
git-subtree-mainline: 464bbcb15c
git-subtree-split: 24f5a642af
Change-Id: I6105b3762b79126b3488359c95978cadb3efa789

users/wpcarro/scratch/deepmind/part_two/nth-fibonacci.py

@@ -0,0 +1,72 @@
+import unittest
+
+
+# Compute the fibonacci using a bottom-up algorithm.
+def fib(n):
+    if n < 0:
+        raise Error('Cannot call fibonacci with negative values')
+    cache = [0, 1]
+    for i in range(n):
+        cache[0], cache[1] = cache[1], cache[0] + cache[1]
+    return cache[0]
+
+
+# Compute the fibonacci using memoization.
+def fib_memoized(n):
+    cache = {
+        0: 0,
+        1: 1,
+    }
+
+    def do_fib(n):
+        if n < 0:
+            raise Error('The fib function does not support negative inputs')
+
+        if n in cache:
+            return cache[n]
+
+        cache[n - 1] = do_fib(n - 1)
+        cache[n - 2] = do_fib(n - 2)
+        return cache[n - 1] + cache[n - 2]
+
+    return do_fib(n)
+
+
+# Tests
+class Test(unittest.TestCase):
+    def test_zeroth_fibonacci(self):
+        actual = fib(0)
+        expected = 0
+        self.assertEqual(actual, expected)
+
+    def test_first_fibonacci(self):
+        actual = fib(1)
+        expected = 1
+        self.assertEqual(actual, expected)
+
+    def test_second_fibonacci(self):
+        actual = fib(2)
+        expected = 1
+        self.assertEqual(actual, expected)
+
+    def test_third_fibonacci(self):
+        actual = fib(3)
+        expected = 2
+        self.assertEqual(actual, expected)
+
+    def test_fifth_fibonacci(self):
+        actual = fib(5)
+        expected = 5
+        self.assertEqual(actual, expected)
+
+    def test_tenth_fibonacci(self):
+        actual = fib(10)
+        expected = 55
+        self.assertEqual(actual, expected)
+
+    def test_negative_fibonacci(self):
+        with self.assertRaises(Exception):
+            fib(-1)
+
+
+unittest.main(verbosity=2)