81 lines
2.4 KiB
Python
81 lines
2.4 KiB
Python
"""
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Aho-Corasick Algorithm
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Author: Wenru Dong
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"""
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from collections import deque
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from typing import List
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class ACNode:
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def __init__(self, data: str):
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self._data = data
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self._children = [None] * 26
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self._is_ending_char = False
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self._length = -1
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self._suffix = None
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class ACAutomata:
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def __init__(self):
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self._root = ACNode("/")
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def _build_suffix_link(self) -> None:
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q = deque()
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q.append(self._root)
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while q:
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node = q.popleft()
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for child in node._children:
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if child:
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if node == self._root:
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child._suffix = self._root
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else:
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suffix = node._suffix
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while suffix:
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suffix_child = suffix._children[ord(child._data) - ord("a")]
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if suffix_child:
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child._suffix = suffix_child
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break
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suffix = suffix._suffix
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if not suffix:
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child._suffix = self._root
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q.append(child)
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def _insert(self, text: str) -> None:
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node = self._root
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for index, char in map(lambda x: (ord(x) - ord("a"), x), text):
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if not node._children[index]:
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node._children[index] = ACNode(char)
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node = node._children[index]
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node._is_ending_char = True
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node._length = len(text)
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def insert(self, patterns: List[str]) -> None:
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for pattern in patterns:
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self._insert(pattern)
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self._build_suffix_link()
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def match(self, text: str) -> None:
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node = self._root
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for i, char in enumerate(text):
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index = ord(char) - ord("a")
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while not node._children[index] and node != self._root:
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node = node._suffix
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node = node._children[index]
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if not node:
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node = self._root
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tmp = node
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while tmp != self._root:
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if tmp._is_ending_char:
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print(f"匹配起始下标{i - tmp._length + 1}，长度{tmp._length}")
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tmp = tmp._suffix
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if __name__ == "__main__":
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patterns = ["at", "art", "oars", "soar"]
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ac = ACAutomata()
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ac.insert(patterns)
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ac.match("soarsoars")
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