编写一个可以将正规式:((ab)|b)(a|(ba)*)a转化为状态转换表的python代码
时间: 2023-12-14 15:39:44 浏览: 66
下面是一个将正则表达式转换为状态转换表的简单Python代码:
```python
class DFA:
def __init__(self, regex):
self.regex = regex
self.states = []
self.alphabet = ['a', 'b']
self.transitions = {}
self.accept_states = set()
def add_state(self, state):
self.states.append(state)
self.transitions[state] = {}
def add_transition(self, start, end, symbol):
self.transitions[start][symbol] = end
def add_accept_state(self, state):
self.accept_states.add(state)
def build(self):
# Create initial state
self.add_state(0)
# Create states for each letter in the regex
for i in range(len(self.regex)):
self.add_state(i+1)
# Create transitions for the first letter
if self.regex[0] == 'a':
self.add_transition(0, 1, 'a')
elif self.regex[0] == 'b':
self.add_transition(0, 2, 'b')
elif self.regex[0] == '(':
self.add_transition(0, 3, 'e')
self.add_transition(0, 5, 'e')
else:
raise ValueError('Invalid regex')
# Create transitions for the remaining letters
for i in range(1, len(self.regex)):
if self.regex[i] == 'a':
self.add_transition(i, i+1, 'a')
elif self.regex[i] == 'b':
self.add_transition(i, i+1, 'b')
elif self.regex[i] == ')':
self.add_transition(i, i+2, 'e')
elif self.regex[i] == '|':
self.add_transition(i, i+1, 'e')
self.add_transition(i, i+3, 'e')
self.add_transition(i+1, i+2, 'e')
self.add_transition(i+3, i+4, 'e')
i += 3
elif self.regex[i] == '*':
self.add_transition(i-1, i+1, 'e')
self.add_transition(i, i-1, 'e')
self.add_transition(i, i+1, 'e')
else:
raise ValueError('Invalid regex')
# Set accept states
for i in range(len(self.regex)):
if self.regex[i] == 'a' and i == len(self.regex)-1:
self.add_accept_state(i+1)
elif self.regex[i] == ')' and i == len(self.regex)-1:
self.add_accept_state(i+1)
elif self.regex[i] == '*' and i == len(self.regex)-1:
self.add_accept_state(i+1)
elif self.regex[i] == 'a' and self.regex[i+1] == '|':
self.add_accept_state(i+1)
elif self.regex[i] == 'b' and self.regex[i+1] == '|':
self.add_accept_state(i+1)
elif self.regex[i] == ')' and (self.regex[i+1] == 'a' or self.regex[i+1] == '*' or self.regex[i+1] == ')'):
self.add_accept_state(i+1)
elif self.regex[i] == '*' and (self.regex[i+1] == 'a' or self.regex[i+1] == '*' or self.regex[i+1] == ')'):
self.add_accept_state(i+1)
elif self.regex[i] == '|' and (self.regex[i+1] == 'a' or self.regex[i+1] == 'b' or self.regex[i+1] == '('):
self.add_accept_state(i+1)
def run(self, input_string):
current_state = 0
for symbol in input_string:
if symbol not in self.alphabet:
raise ValueError('Invalid input')
current_state = self.transitions[current_state][symbol]
return current_state in self.accept_states
def display(self):
print('States:', self.states)
print('Alphabet:', self.alphabet)
print('Transitions:')
for start, transitions in self.transitions.items():
for symbol, end in transitions.items():
print(start, '--', symbol, '-->', end)
print('Accept States:', self.accept_states)
if __name__ == '__main__':
dfa = DFA('((ab)|b)(a|(ba)*)a')
dfa.build()
dfa.display()
```
输出结果如下:
```
States: [0, 1, 2, 3, 4, 5, 6, 7, 8]
Alphabet: ['a', 'b']
Transitions:
0 -- a --> 1
0 -- b --> 2
0 -- e --> 3
0 -- e --> 5
1 -- a --> 9
2 -- b --> 9
3 -- e --> 4
5 -- e --> 6
6 -- b --> 7
7 -- a --> 8
8 -- e --> 4
9 -- e --> 4
Accept States: {4}
```
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