about summary refs log tree commit diff
path: root/users/wpcarro/scratch/data_structures_and_algorithms/perm-tree.py
diff options
context:
space:
mode:
authorVincent Ambo <mail@tazj.in>2021-12-13T22·51+0300
committerVincent Ambo <mail@tazj.in>2021-12-13T23·15+0300
commit019f8fd2113df4c5247c3969c60fd4f0e08f91f7 (patch)
tree76a857f61aa88f62a30e854651e8439db77fd0ea /users/wpcarro/scratch/data_structures_and_algorithms/perm-tree.py
parent464bbcb15c09813172c79820bcf526bb10cf4208 (diff)
parent6123e976928ca3d8d93f0b2006b10b5f659eb74d (diff)
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
Diffstat (limited to 'users/wpcarro/scratch/data_structures_and_algorithms/perm-tree.py')
-rw-r--r--users/wpcarro/scratch/data_structures_and_algorithms/perm-tree.py83
1 files changed, 83 insertions, 0 deletions
diff --git a/users/wpcarro/scratch/data_structures_and_algorithms/perm-tree.py b/users/wpcarro/scratch/data_structures_and_algorithms/perm-tree.py
new file mode 100644
index 000000000000..0eb389c26bb9
--- /dev/null
+++ b/users/wpcarro/scratch/data_structures_and_algorithms/perm-tree.py
@@ -0,0 +1,83 @@
+import unittest
+
+
+################################################################################
+# Answer
+################################################################################
+class Node(object):
+    def __init__(self, value, children=set()):
+        self.value = value
+        self.children = children
+
+
+# treeify :: Char -> Set(Char) -> Node(Char)
+def treeify(x, xs):
+    return Node(x, [treeify(c, xs - {c}) for c in xs])
+
+
+# dft :: Node(Char) -> [String]
+def dft(node):
+    result = []
+    s = []
+
+    s.append(('', node))
+
+    while s:
+        p, n = s.pop()
+        p += str(n.value)
+
+        if not n.children:
+            result.append(p)
+        else:
+            for c in n.children:
+                s.append((p, c))
+
+    return result
+
+
+# main :: String -> Set(String)
+def get_permutations(xs):
+    if xs == '':
+        return set([''])
+
+    ys = set(xs)
+    trees = []
+
+    for y in ys:
+        trees.append(treeify(y, ys - {y}))
+
+    result = set()
+
+    for t in trees:
+        for d in dft(t):
+            result.add(d)
+
+    return result
+
+
+################################################################################
+# 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)