class Queue:
def __init__(self):
self.stack = Stack()
def enqueue(self, value):
self.stack.push(value)
return True
def dequeue(self):
stack1 = Stack()
stack2 = Stack()
# 通过两个栈 反转栈 得到第一个
for _ in range(self.stack.size() - 1):
stack1.push(self.stack.pop())
for _ in range(stack1.size()):
stack2.push(stack1.pop())
value = self.stack.pop() # 弹出第一个
self.stack = stack2
return value
def is_empty(self) -> bool:
return self.stack.size()
def size(self) -> int:
return self.stack.size()
def reverse_string(str):
temp = Stack()
str2 = []
for i in str:
temp.push(i)
print(temp.size())
i = 0
while temp.size() > 0:
str2.append(temp.pop())
return str2
def isValid(self, s):
"""
:type s: str
:rtype: bool
"""
# valid parentheses
# first check empty string
if len(s) == 0:
return True
# using stack for check parentheses
stack = Stack() # call for a stack structure
for i in s:
if i in ['{', '[', '(']:
stack.push(i)
elif i in ['}', ']', ')']:
if stack.size() == 0:
return False
chFromstack = stack.pop()
if not ((chFromstack == '{' and i == '}') or
(chFromstack == '[' and i == ']') or
(chFromstack == '(' and i == ')')):
# one of the above conditions
return False
return stack.isEmpty()
def dequeue(self):
stack1 = Stack()
stack2 = Stack()
# 通过两个栈 反转栈 得到第一个
for _ in range(self.stack.size() - 1):
stack1.push(self.stack.pop())
for _ in range(stack1.size()):
stack2.push(stack1.pop())
value = self.stack.pop() # 弹出第一个
self.stack = stack2
return value