def infixToPostfix(infixexpr):
opstack = Stack() # 创建空栈
result = [] # 结果的列表
prec = {'*': 3, '/': 3, '+': 2, '-': 2, '(': 1} # 运算符的优先级
operator_list = ['+', '-', '*', '/']
for token in tolist(infixexpr):
if token.capitalize() in string.ascii_uppercase: # 判断是否是操作数
result.append(token.capitalize())
else:
if token == '(': # 判断是是否是左括号
opstack.push(token)
elif token == ')': # 判断是否是右括号
topToken = opstack.pop()
while topToken != '(':
result.append(topToken)
topToken = opstack.pop()
elif token in operator_list: # 判断是否是运算符
while not opstack.isEmpty() and (prec[opstack.peek()] >= prec[token]):
result.append(opstack.pop())
opstack.push(token)
else:
pass
while not opstack.isEmpty():
result.append(opstack.pop())
return "".join(result)
def infixToPostfix(infixexpr):
# 记录操作符优先级
prec = {}
prec["*"] = 3
prec["/"] = 3
prec["+"] = 2
prec["-"] = 2
prec["("] = 1
# 初始化栈
opStack = Stack()
postfixList = []
# 将表达式转为单词列表
tokenList = infixexpr.split()
for token in tokenList:
if token in "ABCDEFGHIJKLMNOPQRSTUVWXYZ" or token in "0123456789":
postfixList.append(token)
elif token == '(':
opStack.push(token)
elif token == ')':
topToken = opStack.pop()
while topToken != '(':
postfixList.append(topToken)
topToken = opStack.pop()
else:
while (not opStack.isEmpty()) and (prec[opStack.peek()] >=
prec[token]):
postfixList.append(opStack.pop())
opStack.push(token)
while not opStack.isEmpty():
postfixList.append(opStack.pop())
return " ".join(postfixList)