class Buffer:
def __init__(self):
self.__right = Stack()
self.__left = Stack()
self.__N = 0
def insert(self, c):
self.__right.push(c)
self.__N += 1
def delete(self):
self.__N -= 1
return self.__right.pop() if not self.__right.is_empty() else ''
def left(self, k):
for i in range(k):
if self.__left.is_empty():
return
self.__right.push(self.__left.pop())
def right(self, k):
for i in range(k):
if self.__right.is_empty():
return
self.__left.push(self.__right.pop())
def size(self):
return self.__N
def parentheses(test_str):
s = Stack()
for i in test_str:
if i in right_parenthesis:
s.push(i)
else:
pop = s.pop()
if not ord(pop) - ord(i) <= 2: # 比较ascii数值，小于等于2的话就是匹配的左括号
return False
return s.is_empty()
operator_precedence = {'+': 1, '-': 1, '*': 2, '/': 2}
res_str = ''
def not_greater(this, peek):
try:
a = operator_precedence[this]
b = operator_precedence[peek]
return True if a <= b else False
except KeyError:
return False
for i in test_str_list:
if i.isnumeric():
res_str += i + ' '
elif i == '(':
operator_stack.push(i)
elif i == ')':
while not operator_stack.is_empty() and operator_stack.peek() != '(':
res_str += operator_stack.pop() + ' '
operator_stack.pop()
else:
while not operator_stack.is_empty() and not_greater(i, operator_stack.peek()):
res_str += operator_stack.pop() + ' '
operator_stack.push(i)
while not operator_stack.is_empty():
res_str += operator_stack.pop()
print(res_str)