python实现双向循环链表

参考https://www.cnblogs.com/symkmk123/p/9693872.html#4080149

# -*- coding:utf-8 -*-
# __author__ :kusy
# __content__:双向循环链表实现
# __date__:2018/9/29 16:34


# 节点类
class DNode(object):
    def __init__(self, prev, next, value):
        self.prev = prev    # 前驱
        self.next = next    # 后继
        self.value = value  # 值


class DoubleLinkTable(object):
    def __init__(self):
        self.nCount = 0     # 节点个数
        self.nHead = DNode(None, None, None)    # 表头
        self.nHead.prev = self.nHead    # 表头的前驱后继都是自己
        self.nHead.next = self.nHead    # 表头的前驱后继都是自己
        self.node = self.nHead

    # 节点数目
    def size(self):
        return self.nCount

    # 判断链表是否为空
    def is_empty(self):
        return self.nCount == 0

    # 获取index位置的节点
    def getnode(self, index):
        if index == 0:
            return self.nHead
        if index < 0 or index > self.nCount:
            raise Exception('IndexOutOfBounds')

        # 二分正向查找
        if index < self.nCount / 2:
            self.node = self.nHead.next
            i = 0
            while i < index - 1:
                self.node = self.node.next
                i += 1
            return self.node
        # 反向查找剩余部分
        self.node = self.nHead.prev
        rindex = self.nCount - index
        j = 0
        while j < rindex:
            self.node = self.node.prev
            j = j + 1
        return self.node

    # 获取index位置节点的值
    def get(self, index):
        return self.getnode(index).value

    # 插入新节点（后插）
    def insert(self, index, value):
        now_node = self.getnode(index)
        new_node = DNode(None,None,value)
        new_node.prev = now_node
        new_node.next = now_node.next
        now_node.next.prev = new_node
        now_node.next = new_node
        self.nCount += 1

    # 删除节点
    def delete(self, index):
        if index == 0:
            raise Exception('0 is not allowed!')
        now_node = self.getnode(index)
        now_node.prev.next = now_node.next
        now_node.next.prev = now_node.prev
        self.nCount -= 1

if __name__ == '__main__':
    dlt = DoubleLinkTable()
    # 头节点下标为0
    dlt.insert(0, 12)
    dlt.insert(1, 13)
    dlt.insert(1, 14)
    print('---------------------------')
    for i in range(dlt.nCount+1):
        print(i, ':', dlt.get(i))
    print('size:', dlt.nCount)

    dlt.delete(2)
    print('-------after delete--------')
    for i in range(dlt.nCount+1):
        print(i, ':', dlt.get(i))
    print('size:', dlt.nCount)

执行结果如下

C:UserssuneeeAppDataLocalProgramsPythonPython36python.exe E:/wangjz/PyWorkSpace/LearnPython/PY0929/double_linktable.py
---------------------------
0 : None
1 : 12
2 : 14
3 : 13
size: 3
-------after delete--------
0 : None
1 : 12
2 : 13
size: 2

Process finished with exit code 0

数据分析如下图