def infix2postfix(infix):
prec = {
'(': 1,
'+': 2,
'-': 2,
'*': 3,
'/': 3,
}
stack = Stack()
infix_list, postfix_list = infix.split(), []
for char in infix_list:
if char in string.ascii_uppercase:
postfix_list.append(char)
elif char == '(':
stack.push(char)
elif char == ')':
token = stack.pop()
while token != '(':
postfix_list.append(token)
token = stack.pop()
else:
while not stack.is_empty() and prec[stack.peek()] >= prec[char]:
postfix_list.append(stack.pop())
stack.push(char)
while not stack.is_empty():
postfix_list.append(stack.pop())
return ' '.join(postfix_list)
def par_checker(symbol_string):
stack = Stack()
idx, n, balanced = 0, len(symbol_string), True
while idx < n and balanced:
symbol = symbol_string[idx]
if symbol in '([{':
stack.push(symbol)
else:
if stack.is_empty() or not matches(stack.pop(), symbol):
balanced = False
idx += 1
if balanced and stack.is_empty():
return True
else:
return False
def par_checker(symbol_string):
stack = Stack()
index, length, balanced = 0, len(symbol_string), True
while index < length and balanced:
symbol = symbol_string[index]
if symbol == '(':
stack.push(symbol)
else:
if stack.is_empty():
balanced = False
else:
stack.pop()
index += 1
if balanced and stack.is_empty():
return True
else:
return False
def htmlChecker(htmlStr):
stack = Stack()
hsize = len(htmlStr)
i = 0
while i < hsize:
tag = []
openTag = True
if htmlStr[i] == '<':
tag.append('<')
i += 1
if htmlStr[i] == '/':
openTag = False
i += 1
while (i < hsize) and htmlStr[i] == ' ':
i += 1
while (i < hsize) and (htmlStr[i].isalpha()
or htmlStr[i].isdigit()):
tag.append(htmlStr[i])
i += 1
while (i < hsize) and htmlStr[i] != '>':
i += 1
if (i >= hsize):
return False
tag.append(htmlStr[i])
htmTag = ''.join(tag)
# print ("tag: ", htmTag)
if openTag:
stack.push(htmTag)
elif stack.is_empty():
return False
else:
topTag = stack.pop()
# print("popped: ", topTag)
# print("htmTag: ", htmTag)
if topTag != htmTag:
return False
i += 1
if not stack.is_empty():
return False
return True
def decimal2bin(decimal_number):
stack = Stack()
while decimal_number > 0:
rem = decimal_number % 2
stack.push(rem)
decimal_number //= 2
res_list = []
while not stack.is_empty():
res_list.append(str(stack.pop()))
return ''.join(res_list)
def base_converter(decimal_number, base=10):
digits = '0123456789ABCDEF'
assert base <= 16
stack = Stack()
while decimal_number > 0:
rem = decimal_number % base
stack.push(rem)
decimal_number //= base
res_list = []
while not stack.is_empty():
res_list.append(digits[stack.pop()])
return ''.join(res_list)
def _search(self, key, on_delete=False):
"""
跳表 search/insert/delete 方法通用查询逻辑
Args:
key: 查询的键
on_delete: delete方法特有逻辑
Returns:
目标节点, 目标节点的前驱节点列表
"""
node: Union[HeaderNode, DataNode] = self._head
tower_stack = Stack() # 前驱节点列表（通过栈维护由底向上的顺序）
found = False
while node is not None and not found:
if node.next is None or node.next.key > key:
tower_stack.push(node) # 降到下一层前保存当前层的前驱节点
node = node.down
elif node.next.key <= key:
node = node.next
if node.key == key:
found = True
if found and on_delete:
# 删除操作中，需要继续往下找到每一层目标节点的前驱节点
pre_node = self._head if tower_stack.is_empty(
) else tower_stack.pop()
while pre_node is not None:
if pre_node.next is None or pre_node.next.key >= key:
tower_stack.push(pre_node)
pre_node = pre_node.down
else:
pre_node = pre_node.next
return node, tower_stack
