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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/facebook/recursive-string-permutations.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/facebook/recursive-string-permutations.py')
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diff --git a/users/wpcarro/scratch/facebook/recursive-string-permutations.py b/users/wpcarro/scratch/facebook/recursive-string-permutations.py
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+++ b/users/wpcarro/scratch/facebook/recursive-string-permutations.py
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+# permutations: no repeat characters
+
+def char_and_rest(i, xs):
+    return xs[i], xs[0:i] + xs[i + 1:]
+
+def permutations(xs):
+    if len(xs) == 1:
+        return [xs]
+    result = []
+    for c, rest in [char_and_rest(i, xs) for i in range(len(xs))]:
+        result += [c + perm for perm in permutations(rest)]
+    return result
+
+expected = ["cat", "cta", "act", "atc", "tca", "tac"]
+result = permutations("cat")
+print(result, expected)
+assert len(result) == len(expected)
+assert result == expected
+print("Success!")