class QueueTwoStack:
def __init__(self):
self.stack1 = Stack()
self.stack2 = Stack()
def enqueue(self, n):
self.stack1.push(n)
def dequeue(self):
if self.stack2.isEmpty():
while not self.stack1.isEmpty():
self.stack2.push(self.stack1.pop())
return self.stack2.pop()
def eval_postfix(exp):
n = len(exp)
if n < 1:
return None
stack = Stack()
for i in range(n - 1, -1, -1):
if isOperand(exp[i]):
stack.push(exp[i])
else:
ele1 = stack.pop()
ele2 = stack.pop()
print(ele1, ele2, exp[i])
n = eval(ele2 + exp[i] + ele1)
stack.push(str(int(n)))
result = stack.pop()
return result
class QueueOneStack:
def __init__(self):
self.stack = Stack()
def enqueue(self, n):
self.stack.push(n)
def dequeue(self):
if self.stack.isEmpty():
return None
node = self.stack.pop()
if self.stack.isEmpty():
print(node)
else:
self.dequeue()
self.stack.push(node)
def validatePren(data):
stack = Stack()
opening = set('([{')
closing = set(')]}')
matches = {
')' : '(',
']' : '[',
'}' : '{'
}
for i in data:
if i in opening:
stack.push(i)
elif i in closing:
last = stack.pop()
if matches[i] != last:
return False
if stack.isEmpty():
return True
return False
def __init__(self):
self.stack1 = Stack()
self.stack2 = Stack()
def __init__(self):
self.stack = Stack()
class StackWithMin:
def __init__(self):
self.stack = Stack()
self.minStack = Stack()
def push(self, n):
cur = self.minStack.peek()
if cur is None or cur > n:
self.stack.push(n)
self.minStack.push(n)
else:
self.stack.push(n)
self.minStack.push(cur)
def pop(self):
tmp = self.stack.pop()
min = self.minStack.pop()
return tmp
def getMin(self):
return self.minStack.peek()