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, 33 insertions, 0 deletions

diff --git a/users/wpcarro/scratch/facebook/product-of-all-other-numbers.py b/users/wpcarro/scratch/facebook/product-of-all-other-numbers.py
new file mode 100644
index 000000000000..d381386b6257
--- /dev/null
+++ b/users/wpcarro/scratch/facebook/product-of-all-other-numbers.py
@@ -0,0 +1,33 @@
+from random import randint
+from math import floor
+
+# loop {forwards, backwards, up, down}
+# through a table of values, [[a]].
+
+def product(xs):
+    n = len(xs)
+    lhs = [1] * (n + 1)
+    for i in range(1, n):
+        lhs[i] = lhs[i - 1] * xs[i - 1]
+    rhs = [1] * (n + 1)
+    for i in range(n - 1, 0, -1):
+        rhs[i] = rhs[i + 1] * xs[i]
+    result = []
+    for i in range(n):
+        result.append(lhs[i] * rhs[i + 1])
+    return result
+
+def computed_expected(xs):
+    product = 1
+    for x in xs:
+        product *= x
+    return [floor(product / x) for x in xs]
+
+xs = [randint(1, 10) for _ in range(5)]
+expected = computed_expected(xs)
+result = product(xs)
+print(xs, result, expected)
+assert result == expected
+print("Success!")
+
+print(product([2, 4, 3, 10, 5]))