'''
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.stack = []
        self.min = None

    def push(self, x):
        """
        :type x: int
        :rtype: void
        """
        self.stack.append(x)
        if self.min == None or self.min > x:
            self.min = x

    def pop(self):
        """
        :rtype: void
        """

        popItem = self.stack.pop()
        if len(self.stack) == 0:
            self.min = None
            return popItem

        if popItem == self.min:
            self.min = self.stack[0]
            for i in self.stack:
                if i < self.min:
                    self.min = i
        return popItem

    def top(self):
        """
        :rtype: int
        """
        return self.stack[-1]

    def getMin(self):
        """
        :rtype: int
        """
        return self.min

if __name__ == "__main__":
    minStack = MinStack()
    minStack.push(-2)
    minStack.push(0)
    minStack.push(-3)
    print(minStack.getMin())
    minStack.pop()
    print(minStack.top())
    print(minStack.getMin())



#ok