69 lines
1.7 KiB
Python
69 lines
1.7 KiB
Python
import typing as t
|
|
|
|
key = t.Sequence[t.Hashable]
|
|
|
|
|
|
def new_trie(keywords: t.Iterable[key]) -> t.Dict:
|
|
"""
|
|
Creates a new trie out of a collection of keywords.
|
|
|
|
The trie is represented as a sequence of nested dictionaries keyed by either single character
|
|
strings, or by 0, which is used to designate that a keyword is in the trie.
|
|
|
|
Example:
|
|
>>> new_trie(["bla", "foo", "blab"])
|
|
{'b': {'l': {'a': {0: True, 'b': {0: True}}}}, 'f': {'o': {'o': {0: True}}}}
|
|
|
|
Args:
|
|
keywords: the keywords to create the trie from.
|
|
|
|
Returns:
|
|
The trie corresponding to `keywords`.
|
|
"""
|
|
trie: t.Dict = {}
|
|
|
|
for key in keywords:
|
|
current = trie
|
|
|
|
for char in key:
|
|
current = current.setdefault(char, {})
|
|
current[0] = True
|
|
|
|
return trie
|
|
|
|
|
|
def in_trie(trie: t.Dict, key: key) -> t.Tuple[int, t.Dict]:
|
|
"""
|
|
Checks whether a key is in a trie.
|
|
|
|
Examples:
|
|
>>> in_trie(new_trie(["cat"]), "bob")
|
|
(0, {'c': {'a': {'t': {0: True}}}})
|
|
|
|
>>> in_trie(new_trie(["cat"]), "ca")
|
|
(1, {'t': {0: True}})
|
|
|
|
>>> in_trie(new_trie(["cat"]), "cat")
|
|
(2, {0: True})
|
|
|
|
Args:
|
|
trie: the trie to be searched.
|
|
key: the target key.
|
|
|
|
Returns:
|
|
A pair `(value, subtrie)`, where `subtrie` is the sub-trie we get at the point where the search stops, and `value`
|
|
is either 0 (search was unsuccessfull), 1 (`value` is a prefix of a keyword in `trie`) or 2 (`key is in `trie`).
|
|
"""
|
|
if not key:
|
|
return (0, trie)
|
|
|
|
current = trie
|
|
|
|
for char in key:
|
|
if char not in current:
|
|
return (0, current)
|
|
current = current[char]
|
|
|
|
if 0 in current:
|
|
return (2, current)
|
|
return (1, current)
|