mirror of
https://github.com/TheAlgorithms/Python.git
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93 lines
3.3 KiB
Python
93 lines
3.3 KiB
Python
from collections import deque
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class Automaton:
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def __init__(self, keywords):
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self.adlist = list()
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self.adlist.append(
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{"value": "", "next_states": [], "fail_state": 0, "output": []}
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)
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for keyword in keywords:
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self.add_keyword(keyword)
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self.set_fail_transitions()
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def find_next_state(self, current_state, char):
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for state in self.adlist[current_state]["next_states"]:
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if char == self.adlist[state]["value"]:
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return state
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return None
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def add_keyword(self, keyword):
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current_state = 0
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for character in keyword:
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if self.find_next_state(current_state, character):
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current_state = self.find_next_state(current_state, character)
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else:
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self.adlist.append(
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{
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"value": character,
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"next_states": [],
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"fail_state": 0,
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"output": [],
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}
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)
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self.adlist[current_state]["next_states"].append(len(self.adlist) - 1)
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current_state = len(self.adlist) - 1
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self.adlist[current_state]["output"].append(keyword)
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def set_fail_transitions(self):
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q = deque()
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for node in self.adlist[0]["next_states"]:
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q.append(node)
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self.adlist[node]["fail_state"] = 0
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while q:
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r = q.popleft()
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for child in self.adlist[r]["next_states"]:
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q.append(child)
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state = self.adlist[r]["fail_state"]
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while (
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self.find_next_state(state, self.adlist[child]["value"]) == None
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and state != 0
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):
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state = self.adlist[state]["fail_state"]
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self.adlist[child]["fail_state"] = self.find_next_state(
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state, self.adlist[child]["value"]
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)
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if self.adlist[child]["fail_state"] == None:
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self.adlist[child]["fail_state"] = 0
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self.adlist[child]["output"] = (
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self.adlist[child]["output"]
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+ self.adlist[self.adlist[child]["fail_state"]]["output"]
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)
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def search_in(self, string):
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"""
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>>> A = Automaton(["what", "hat", "ver", "er"])
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>>> A.search_in("whatever, err ... , wherever")
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{'what': [0], 'hat': [1], 'ver': [5, 25], 'er': [6, 10, 22, 26]}
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"""
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result = dict() # returns a dict with keywords and list of its occurences
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current_state = 0
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for i in range(len(string)):
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while (
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self.find_next_state(current_state, string[i]) == None
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and current_state != 0
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):
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current_state = self.adlist[current_state]["fail_state"]
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current_state = self.find_next_state(current_state, string[i])
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if current_state is None:
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current_state = 0
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else:
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for key in self.adlist[current_state]["output"]:
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if not (key in result):
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result[key] = []
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result[key].append((i - len(key) + 1))
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return result
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if __name__ == "__main__":
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import doctest
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doctest.testmod()
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