python实现双向链表

p y t h o n 实 现 双 向 链 表 python实现双向链表 python实现双向链表

练习三部曲之一

# 1.节点构造
class Node(object):
    def __init__(self, elem):
        self.elem = elem
        self.pre = None
        self.next = None


class DoubleLinkedList(object):
    # 2.成员构造
    def __init__(self, node=None):
        self.__head = node

    # 3.返回大小
    def length(self):
        cur = self.__head
        count = 0
        while cur is not None:
            count += 1
            cur = cur.next
        return count

    # 4.判空
    def is_empty(self):
        return self.__head is None

    # 5.增
    def addFirst(self, elem):
        node = Node(elem)
        if self.is_empty():  # 链表为空
            self.__head = node
        else:
            node.next = self.__head
            node.next.pre = node
            self.__head = node

    def addLast(self, elem):
        node = Node(elem)
        if self.is_empty():
            self.__head = node
        else:
            cur = self.__head
            while cur.next is not None:
                cur = cur.next
            cur.next = node
            node.pre = cur

    def add(self, pos, elem):
        if pos == 0:
            self.addFirst(elem)
        elif pos > self.length() or pos < 0:
            raise ValueError('Add failed. Illegal index.')
        else:
            node = Node(elem)
            cur = self.__head
            pre = None
            for i in range(pos):
                pre = cur
                cur = cur.next
            pre.next = node
            node.pre = pre
            node.next = cur
            if cur:
                cur.pre = node
    # 6.删
    def remove(self, elem):
        if self.is_empty():
            return
        cur = self.__head
        while cur is not None:
            if cur.elem == elem:
                if cur == self.__head:  # 若是头结点
                    self.__head = cur.next  # 链表中只有一个结点
                    if cur.next:
                        cur.next.pre = None
                else:
                    cur.pre.next = cur.next
                    if cur.next:  # 如果不是尾结点
                        cur.next.pre = cur.pre
                break
            else:
                cur = cur.next

    # 7.查
    def travel(self):
        cur = self.__head
        while cur is not None:
            print(cur.elem, end=' ')
            cur = cur.next
        
    def search(self, elem):
        cur = self.__head
        while cur is not None:
            if cur.elem == elem:
                return True
            else:
                cur = cur.next
        return False

练习三部曲之二

# 1.节点构造
class Node(object):
    def __init__(self, elem):


class DoubleLinkedList(object):
    # 2.成员构造
    def __init__(self, node=None):

    # 3.返回大小
    def length(self):

    # 4.判空
    def is_empty(self):

    # 5.增
    def addFirst(self, elem):

    def addLast(self, elem):

    def add(self, pos, elem):

    # 6.删
    def remove(self, elem):

    # 7.查
    def travel(self):


    def search(self, elem):

练习三部曲之三

# 1.节点构造

class DoubleLinkedList(object):
    # 2.成员构造

    # 3.返回大小


    # 4.判空

    # 5.增

    # 6.删


    # 7.查