如何使用堆栈执行以下操作来更改此infix-> postfix：
对待减号操作相反的符号“ ^”作为负号， 并且仅在后缀表示法中可用。此外，将其视为 数字而不是运算。
class Conversion:
def __init__(self, capacity):
self.top = -1
self.capacity = capacity
self.array = []
self.output = []
self.precedence = {'+': 1, '-': 1, '*': 2, '/': 2, '^': 3}
def isEmpty(self):
return True if self.top == -1 else False
def peek(self):
return self.array[-1]
def pop(self):
if not self.isEmpty():
self.top -= 1
return self.array.pop()
else:
return "$"
def push(self, op):
self.top += 1
self.array.append(op)
def isOperand(self, ch):
return ch.isalpha()
def notGreater(self, i):
try:
a = self.precedence[i]
b = self.precedence[self.peek()]
return True if a <= b else False
except KeyError:
return False
def infixToPostfix(self, exp):
for i in exp:
if self.isOperand(i):
self.output.append(i)
elif i == '(':
self.push(i)
elif i == ')':
while (not self.isEmpty()) and self.peek() != '(':
a = self.pop()
self.output.append(a)
if not self.isEmpty() and self.peek() != '(':
return -1
else:
self.pop()
else:
while not self.isEmpty() and self.notGreater(i):
self.output.append(self.pop())
self.push(i)
while not self.isEmpty():
self.output.append(self.pop())
print("".join(self.output))
exp = "(-a + b)"
obj = Conversion(len(exp))
obj.infixToPostfix(exp)
Current output: ab+-
Required output: ^ab+
