subtree(users/wpcarro): docking briefcase at '24f5a642' r/3226

git-subtree-dir: users/wpcarro
git-subtree-mainline: 464bbcb15c09813172c79820bcf526bb10cf4208
git-subtree-split: 24f5a642af3aa1627bbff977f0a101907a02c69f
Change-Id: I6105b3762b79126b3488359c95978cadb3efa789

1 files changed, 68 insertions, 0 deletions

diff --git a/users/wpcarro/scratch/deepmind/part_two/product-of-other-numbers.py b/users/wpcarro/scratch/deepmind/part_two/product-of-other-numbers.py
new file mode 100644
index 000000000000..6f7858ff4e5b
--- /dev/null
+++ b/users/wpcarro/scratch/deepmind/part_two/product-of-other-numbers.py
@@ -0,0 +1,68 @@
+import unittest
+
+
+# get_products_of_all_ints_except_at_index :: [Int] -> [Int]
+def get_products_of_all_ints_except_at_index(xs):
+    n = len(xs)
+    if n < 2:
+        raise Exception("Cannot computer without 2 or elements")
+    # lhs
+    befores = [None] * n
+    befores[0] = 1
+    for i in range(1, n):
+        befores[i] = befores[i - 1] * xs[i - 1]
+
+    # rhs
+    afters = [None] * n
+    afters[-1] = 1
+    for i in range(n - 2, -1, -1):
+        afters[i] = afters[i + 1] * xs[i + 1]
+
+    result = [None] * n
+    for i in range(n):
+        result[i] = befores[i] * afters[i]
+    return result
+
+
+# Tests
+class Test(unittest.TestCase):
+    def test_small_list(self):
+        actual = get_products_of_all_ints_except_at_index([1, 2, 3])
+        expected = [6, 3, 2]
+        self.assertEqual(actual, expected)
+
+    def test_longer_list(self):
+        actual = get_products_of_all_ints_except_at_index([8, 2, 4, 3, 1, 5])
+        expected = [120, 480, 240, 320, 960, 192]
+        self.assertEqual(actual, expected)
+
+    def test_list_has_one_zero(self):
+        actual = get_products_of_all_ints_except_at_index([6, 2, 0, 3])
+        expected = [0, 0, 36, 0]
+        self.assertEqual(actual, expected)
+
+    def test_list_has_two_zeros(self):
+        actual = get_products_of_all_ints_except_at_index([4, 0, 9, 1, 0])
+        expected = [0, 0, 0, 0, 0]
+        self.assertEqual(actual, expected)
+
+    def test_one_negative_number(self):
+        actual = get_products_of_all_ints_except_at_index([-3, 8, 4])
+        expected = [32, -12, -24]
+        self.assertEqual(actual, expected)
+
+    def test_all_negative_numbers(self):
+        actual = get_products_of_all_ints_except_at_index([-7, -1, -4, -2])
+        expected = [-8, -56, -14, -28]
+        self.assertEqual(actual, expected)
+
+    def test_error_with_empty_list(self):
+        with self.assertRaises(Exception):
+            get_products_of_all_ints_except_at_index([])
+
+    def test_error_with_one_number(self):
+        with self.assertRaises(Exception):
+            get_products_of_all_ints_except_at_index([1])
+
+
+unittest.main(verbosity=2)