设计一个支持 push，pop，top 操作，并能在常数时间内检索到最小元素的栈。
push(x) – 将元素 x 推入栈中。
pop() – 删除栈顶的元素。
top() – 获取栈顶元素。
getMin() – 检索栈中的最小元素。
示例:
MinStack minStack = new MinStack();
minStack.push(-2);
minStack.push(0);
minStack.push(-3);
minStack.getMin(); --> 返回 -3.
minStack.pop();
minStack.top(); --> 返回 0.
minStack.getMin(); --> 返回 -2.
class MinStack(object):
def __init__(self):
"""
initialize your data structure here.
"""
self.all = []
def push(self, x):
"""
:type x: int
:rtype: None
"""
self.all.append(x)
def pop(self):
"""
:rtype: None
"""
del self.all[-1]
def top(self):
"""
:rtype: int
"""
return self.all[-1]
def getMin(self):
"""
:rtype: int
"""
return min(self.all)
# Your MinStack object will be instantiated and called as such:
# obj = MinStack()
# obj.push(x)
# obj.pop()
# param_3 = obj.top()
# param_4 = obj.getMin()
