題目：

設計一個支援push，pop，top等操作並且可以在O(1)時間內檢索出最小元素的堆疊。

解答：

class MinStack(object):

    def __init__(self):
        """
        initialize your data structure here.
        """
        self.data = []
        self.minValue = []

    def push(self, x):
        """
        :type x: int
        :rtype: void
        """
 

        if not self.data:
            self.data.append(x)
            self.minValue.append(x)
        else:
            self.data.append(x)
            top = self.minValue[-1]
            if x < top:
                self.minValue.append(x)
            else:
                self.minValue.append(top)
 

        

    def pop(self):
        """
        :rtype: void
        """
        if self.data:
            self.minValue.pop()
            return self.data.pop()
        

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

    def
 
 getMin(self):
        """
        :rtype: int
        """
        if self.minValue:
            return self.minValue[-1]
        


# 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()