Leetcode练习(Python):栈类:用栈实现队列:使用栈实现队列的下列操作: push(x) -- 将一个元素放入队列的尾部。 pop() -- 从队列首部移除元素。 peek() -- 返回队列首部的元素。 empty() -- 返回队列是否为空。

题目:

用栈实现队列:使用栈实现队列的下列操作:  push(x) -- 将一个元素放入队列的尾部。 pop() -- 从队列首部移除元素。 peek() -- 返回队列首部的元素。 empty() -- 返回队列是否为空。  

思路:

使用辅助栈。

程序:

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
class MyQueue:
 
    def __init__(self):
        """
        Initialize your data structure here.
        """
        self.myStack = []
        self.myAuxiliaryStack = []
 
    def push(self, x: int) -> None:
        """
        Push element x to the back of queue.
        """
        self.myStack.append(x)
 
    def pop(self) -> int:
        """
        Removes the element from in front of queue and returns that element.
        """
        if self.empty():
            return
        if len(self.myAuxiliaryStack) == 0:
            while len(self.myStack) != 0:
                self.myAuxiliaryStack.append(self.myStack.pop())
            return self.myAuxiliaryStack.pop()
        else:
            return self.myAuxiliaryStack.pop()
 
    def peek(self) -> int:
        """
        Get the front element.
        """
        if self.empty():
            return
        if len(self.myAuxiliaryStack) == 0:
            while len(self.myStack) != 0:
                self.myAuxiliaryStack.append(self.myStack.pop())
            return self.myAuxiliaryStack[-1]
        else:
            return self.myAuxiliaryStack[-1]
 
    def empty(self) -> bool:
        """
        Returns whether the queue is empty.
        """
        if len(self.myStack) == 0 and len(self.myAuxiliaryStack) == 0:
            return True
        else:
            return False
 
# Your MyQueue object will be instantiated and called as such:
# obj = MyQueue()
# obj.push(x)
# param_2 = obj.pop()
# param_3 = obj.peek()
# param_4 = obj.empty()
posted on   桌子哥  阅读(455)  评论(0编辑  收藏  举报
努力加载评论中...

点击右上角即可分享
微信分享提示