双向链表

xiao_liushui

已于 2022-10-19 09:32:44 修改

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CC 4.0 BY-SA版权

文章标签：链表 python 数据结构

于 2019-08-20 16:32:09 首次发布

本文链接：https://blog.youkuaiyun.com/xiao_liushui/article/details/99856184

本文详细介绍了一种数据结构——双向链表的Python实现方法，包括节点定义、基本操作如添加、删除、插入等，并提供了完整的代码示例，有助于理解和掌握双向链表的工作原理。

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'''
双向链表
'''


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

    def __str__(self):
        return str(self.data)


class DoubleList:
    def __init__(self):
        self._head = None

    def isEmpty(self):
        return self._head == None

    def append(self, item):
        # 尾部添加
        node = Node(item)
        if self.isEmpty():
            self._head = node
        else:
            cur = self._head
            while cur.next != None:
                cur = cur.next
            cur.next = node

        # 求长度

    def add(self, item):
        node = Node(item)
        if self.isEmpty():
            self._head = node
        else:
            node.next = self._head
            self._head.prev = node
            self._head = node

    def len(self):
        cur = self._head
        count = 0

        while cur != None:
            count += 1
            cur = cur.next

        return count

    def print_all(self):
        cur = self._head
        while cur != None:
            print(cur)
            cur = cur.next

    def insert(self, index, item):
        if index < 0 or index >= self.len():
            raise IndexError('index Error')
        if index ==0:
            node = Node(item)
            node.next = self._head
            self._head.prve = node
            self._head = node
        else:
            node = Node(item)
            cur = self._head

            while index-1:
                cur = cur.next
                index-=1


        if index == 0:
            node.next = self._head
            self._head = node
        else:
            cur = self._head

            while index - 1:
                cur = cur.next
                index -= 1
            # cur就是index 的前一个节点
            # 设置弄得节点的前一个cur节点
            node.prve = cur
            # 设置node的后一个节点
            node.next = cur.next
            # 设置的是cur的next节点的prve直向node
            cur.next.prev = node
            # 设置cur的next节点就是node
            cur.next = node


    def remove(self, item):
        if self.isEmpty():
            raise ValueError('没有找到该元素')
        else:
            cur = self._head
            if cur.data ==item:
                #删除的是头的节点
                if cur.next ==None:
                    #只有头节点
                    self._head = None
                else:
                    #除了头部节点，还有其他的节点
                    cur.next.prev = None
                    self._head = cur.next
            else:
                while cur !=None:
                    if cur.data == item:
                        cur.prev.next = cur.next
                        cur.next.prev = cur.prev
                        break
                    cur = cur.next

    def update(self, index, item):
        pass


if __name__ == '__main__':
    dlist = DoubleList()

    print(dlist.len())
    print(dlist.isEmpty())

    # dlist.append(6)
    # dlist.append(9)
    # dlist.append(5)
    # print(dlist.len())
    # print(dlist.isEmpty())
    # dlist.print_all()

    dlist.add(6)
    dlist.add(9)
    dlist.add(5)



    dlist.insert(2,55)
    # dlist.remove(55)
    dlist.print_all()

    dlist.remove(6)
    dlist.print_all()