Python的栈和队列实现

栈

class Node:
    def __init__(self, data=None):
        self.next = None    
        self.data = data


class Stack:
    def __init__(self):
        '''初始化'''
        self.top = None
        self.size = 0

    def push(self, data):
        '''将元素压入栈内'''
        node = Node(data)
        if self.top:
            node.next = self.top
            self.top = node
        else:
            self.top = node
        self.size += 1

    def pop(self):
        '''弹出栈顶元素'''
        if self.top:
            data = self.top.data
            self.size -= 1
            if self.top.next:
                self.top = self.top.next
            else:
                self.top = None
            return data
        else:
            return None

    def peek(self):
        '''查看栈顶元素'''
        if self.top:
            return self.top.data
        else:
            return None

队列

class Node:
    def __init__(self, data=None, next=None, prev=None):
        self.data = data
        self.next = next
        self.prev = prev

class Queue:
    def __init__(self):
        self.head = None
        self.tail = None
        self.size = 0

    def enqueue(self, data):
        '''入队'''
        new_node = Node(data, None, None)
        if self.head is None:
            self.head = new_node
            self.tail = self.head
        else:
            new_node.prev = self.tail
            self.tail.next = new_node
            self.tail = new_node
        self.size += 1

    def dequeue(self):
        '''出队'''
        current = self.head
        if self.size == 1:
            self.size -= 1
            self.head = None
            self.tail = None
        elif self.size > 1:
            self.head = self.head.next
            self.head.prev = None
            self.size -= 1

    def iter(self):
        '''遍历队列'''
        current = self.head
        while current:
            data = current.data
            current = current.next
            yield data