def __init__(self, regex):
"""Initializes the NFA from the specified regular expression.
:param regex: the regular expression
"""
self.regex = regex
m = len(regex)
self.m = m
ops = Stack()
graph = Digraph(m + 1)
for i in range(0, m):
lp = i
if regex[i] == "(" or regex[i] == "|":
ops.push(i)
elif regex[i] == ")":
or_ = ops.pop()
# 2-way or operator
if regex[or_] == "|":
lp = ops.pop()
graph.add_edge(lp, or_ + 1)
graph.add_edge(or_, i)
elif regex[or_] == "(":
lp = or_
else:
assert False
if i < m - 1 and regex[i + 1] == "*":
graph.add_edge(lp, i + 1)
graph.add_edge(i + 1, lp)
if regex[i] == "(" or regex[i] == "*" or regex[i] == ")":
graph.add_edge(i, i + 1)
if ops.size() != 0:
raise ValueError("Invalid regular expression")
self.graph = graph
def evaluate():
ops = Stack()
vals = Stack()
while not stdio.isEmpty():
# Read token, push if operator
s = stdio.readString()
if s == "(": pass
elif s == "+": ops.push(s)
elif s == "-": ops.push(s)
elif s == "*": ops.push(s)
elif s == "/": ops.push(s)
elif s == "sqrt": ops.push(s)
elif s == ")":
# Pop, evaluate and push result if token is ")"
op = ops.pop()
v = vals.pop()
if op == "+": v = vals.pop() + v
elif op == "-": v = vals.pop() - v
elif op == "*": v = vals.pop() * v
elif op == "/": v = vals.pop() / v
elif op == "sqrt": v = math.sqrt(v)
vals.push(v)
else:
vals.push(float(s))
stdio.writeln(vals.pop())
def check_syntax(s: str):
stack = Stack()
map_ = {
"(": [0, 1],
"[": [0, 2],
"{": [0, 3],
")": [1, 1],
"]": [1, 2],
"}": [1, 3]
}
for cha in s.strip():
if map_[cha][0] == 0:
stack.push(map_[cha][1])
elif map_[cha][0] == 1:
try:
if stack.peek() == map_[cha][1]:
stack.pop()
else:
return "0"
except:
return "0"
if stack.is_empty() == True:
return "1"
else:
return "0"
def evaluate(expression):
ops = Stack()
vals = Stack()
for char in expression:
if char == '(':
None
elif char == '+':
ops.push('+')
elif char == '-':
ops.push('-')
elif char == '*':
ops.push('*')
elif char == '/':
ops.push('/')
elif char == ')':
op = ops.pop()
v = vals.pop()
if op == '+':
v = vals.pop() + v
elif op == '-':
v = vals.pop() - v
elif op == '*':
v = vals.pop() * v
elif op == '/':
v = vals.pop() / v
vals.push(v)
else:
vals.push(int(char))
#print(f'Operation Stack: {ops}')
#print(f'Value Stack: {vals}')
return vals.pop()
