剑指offer_leetcode_DAY01

1.用栈实现队列功能

python
class CQueue:

    def __init__(self,value=[]):
        self.a=[]
    def appendTail(self, value: int) -> None:
        self.a.append(value)
    
    def deleteHead(self) -> int:
        if not self.a :return -1
        elif self.a:
            return self.a.pop(0)
# Your CQueue object will be instantiated and called as such:
# obj = CQueue()
# obj.appendTail(value)
# param_2 = obj.deleteHead()

2.定义栈的数据结构，请在该类型中实现一个能够得到栈的最小元素的 min 函数在该栈中，调用 min、push 及 pop 的时间复杂度都是 O(1)。

class MinStack:

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


    def push(self, x: int) -> None:
        self.a.append(x)
        if not self.b or self.b[-1]>=x:
            self.b.append(x)
            
    def pop(self) -> None:
        if self.a.pop()==self.b[-1]:
            self.b.pop()

    

    def top(self) -> int:
        return self.a[-1]

        
    def min(self) -> int:
        return self.b[-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.min()