From 5c9079a41059e077f2b71b68eb83ff9fcb2e38d1 Mon Sep 17 00:00:00 2001
From: William Carroll <wpcarro@gmail.com>
Date: Wed, 29 Jan 2020 14:43:20 +0000
Subject: Splice ./universe directory into ./

Manually merging:
- README.md: I added the description from universe/README.md into the heading of
  dotfiles/README.md.
- .envrc: dotfiles/.envrc was a superset of universe/.envrc
- .gitignore: Adding some of the ignored patterns from universe/.gitignore to
  dotfiles/.gitignore

Everything else here should be a simple rename.
---
 deepmind/recursive-string-permutations.py | 56 +++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)
 create mode 100644 deepmind/recursive-string-permutations.py

(limited to 'deepmind/recursive-string-permutations.py')

diff --git a/deepmind/recursive-string-permutations.py b/deepmind/recursive-string-permutations.py
new file mode 100644
index 000000000000..f50db2838707
--- /dev/null
+++ b/deepmind/recursive-string-permutations.py
@@ -0,0 +1,56 @@
+import unittest
+from itertools import permutations
+
+
+class Node(object):
+    def __init__(self, x):
+        self.value = x
+        self.children = []
+
+
+def make_tree(c, xs):
+    root = Node(c)
+    for x in xs:
+        root.children.append(make_tree(x, xs - {x}))
+    return root
+
+
+def get_permutations(xs):
+    xs = set(xs)
+    root = make_tree("", xs)
+    q, perms = [], set()
+    q.append(("", root))
+    while q:
+        c, node = q.pop()
+        if not node.children:
+            perms.add(c)
+        else:
+            for child in node.children:
+                q.append((c + child.value, child))
+    return perms
+
+
+# Tests
+class Test(unittest.TestCase):
+    def test_empty_string(self):
+        actual = get_permutations('')
+        expected = set([''])
+        self.assertEqual(actual, expected)
+
+    def test_one_character_string(self):
+        actual = get_permutations('a')
+        expected = set(['a'])
+        self.assertEqual(actual, expected)
+
+    def test_two_character_string(self):
+        actual = get_permutations('ab')
+        expected = set(['ab', 'ba'])
+        self.assertEqual(actual, expected)
+
+    def test_three_character_string(self):
+        actual = get_permutations('abc')
+        expected = set(['abc', 'acb', 'bac', 'bca', 'cab', 'cba'])
+        self.assertEqual(actual, expected)
+
+
+unittest.main(verbosity=2)
-- 
cgit 1.4.1