这是我第一次在这里提问,我之所以这么做,是因为我在过去的一周里一直在试图弄清楚这个问题,但一直未能解决。我发现了类似的问题,但结果对我没有帮助。我需要一个中缀表达式,用两个堆栈计算结果,一个用于运算符,一个用于数字。例如6 - ( 5 - 3 ) * ( 4 + 2 ) = -6
或{
class NumStack:
def __init__(self):
"""Create an empty stack."""
self._data = [] #nonpublic list instance
def __len__(self):
"""Return the number of elements in the stack."""
return len(self._data)
def is_empty(self):
"""Return True if the stack is empty."""
return len(self._data) == 0
def push(self,e):
"""Add element e to the top of the stack."""
self._data.append(e) #new item stored at end of list
print(self._data)
def top(self):
"""Return (but do not remove) the element at the top of the stack.
Raise Empty exception if the stack is empty"""
if self.is_empty():
return
return self._data[-1] #the last item in the list
def pop(self):
"""Remove and return the element from the top of the stack (i.e, LIFO)
Raise Empty exception if the stack is empty."""
if self.is_empty():
return "empty"
return self._data.pop() #remove last item from list
def str(self):
return self._data
class OperatorStack:
def __init__(self):
"""Create an empty stack."""
self._data = [] #nonpublic list instance
def __len__(self):
"""Return the number of elements in the stack."""
return len(self._data)
def is_empty(self):
"""Return True if the stack is empty."""
length = len(self._data)
if length == 0:
return True
else:
return False
def push(self,e):
"""Add element e to the top of the stack."""
self._data.append(e) #new item stored at end of list
print(self._data)
def top(self):
"""Return (but do not remove) the element at the top of the stack.
Raise Empty exception if the stack is empty"""
if self.is_empty():
return
return self._data[-1] #the last item in the list
def pop(self):
"""Remove and return the element from the top of the stack (i.e, LIFO)
Raise Empty exception if the stack is empty."""
length = len(self)
if length == 0:
print("list is empty")
else:
if self.is_empty():
return
return self._data.pop()
def str(self):
return self._data
def main():
expression = str(input("Enter an expression: "))
expression = expression.split()
print(expression)
N = NumStack()
O = OperatorStack()
new = []
NewOP = []
NewNum = [0,0]
for e in expression:
if e == '(' or e == ')' or e == '+' or e == '-' or e == '*' or e == '/':
O.push(e)
else:
N.push(e)
while O.is_empty() == False or N.is_empty() == False:
TmpOp = O.top()
if TmpOp == ')':
O.pop()
elif TmpOp == '(':
O.pop()
if TmpOp != '(' and TmpOp != ')':
new.append(N.pop())
new.append(O.pop())
print(TmpOp)
while TmpOp == ')':
if N.top() != "empty":
NewNum[1] = N.pop()
if N.top() != "empty":
NewNum[0] = N.top()
print(NewNum[0],NewNum[1])
if O.pop() == '+':
num = float(NewNum[1]) + float(NewNum[0])
new.append(num)
print(num)
O.pop()
break
elif O.pop() == '-':
num = float(NewNum[0]) - float(NewNum[1])
new.append(num)
print(num)
O.pop()
break
elif O.pop() == '*':
num = NewNum[1]*NewNum[0]
new.append(num)
print(num)
# O.pop()
break
elif O.pop() == '/':
num = NewNum[1]/NewNum[0]
new.append(num)
print(num)
# O.pop()
break
if O.top() == ')':
O.pop()
break
if O.__len__() == 0 and N.__len__() == 0:
break
continue
while TmpOp != ')' and TmpOp != '(':
new.append(N.pop())
new.append(O.pop())
print(new)
if O.__len__() == 0 and N.__len__() == 0:
break
print(new)
main()
我相信我的类是正确的,我只是找不到正确提取所需信息的方法。我试着把这些项目放入一个列表中,当我看到一个括号时,我继续进行计算。如果我能把正确的数字写进我的单子里,我就知道我能让它发挥作用。我只需要让“新”包含正确的数字。问题是:"6 - ( 5 - 3 ) * ( 4 + 2 )"
我应该得到[6.0, '*', 2.0, '-', 6]
。这是不可能的。我真的很感激能给我的任何帮助。在
目前没有回答
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