Python数据结构——链表

链表

什么是链表

链表（Linked list）是一种常见的基础数据结构，是一种线性表，但是并不会按线性的顺序存储数据，而是在每一个节点里存到下一个节点的指针(Pointer)。由于不必须按顺序存储，链表在插入的时候可以达到O(1)的复杂度，比另一种线性表顺序表快得多，但是查找一个节点或者访问特定编号的节点则需要O(n)的时间，而顺序表相应的时间复杂度分别是O(logn)和O(1)。

特点

使用链表结构可以克服数组链表需要预先知道数据大小的缺点，链表结构可以充分利用计算机内存空间，实现灵活的内存动态管理。但是链表失去了数组随机读取的优点，同时链表由于增加了结点的指针域，空间开销比较大。

操作

• init():初始化
• insert(): 插入
• trave(): 遍历
• delete(): 删除
• find(): 查找

实现

此处仅实现双向列表

Python

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class LinkedList():     def __init__(self, value=None):         self.value = value         # 前驱         self.before = None         # 后继         self.behind = None       def __str__(self):         if self.value is not None:             return str(self.value)         else:             return 'None'     def init():     return LinkedList('HEAD')     def delete(linked_list):     if isinstance(linked_list, LinkedList):         if linked_list.behind is not None:             delete(linked_list.behind)             linked_list.behind = None             linked_list.before = None         linked_list.value = None     def insert(linked_list, index, node):     node = LinkedList(node)     if isinstance(linked_list, LinkedList):         i = 0         while linked_list.behind is not None:             if i == index:                 break             i += 1             linked_list = linked_list.behind         if linked_list.behind is not None:             node.behind = linked_list.behind             linked_list.behind.before = node         node.before, linked_list.behind = linked_list, node     def remove(linked_list, index):     if isinstance(linked_list, LinkedList):         i = 0         while linked_list.behind is not None:             if i == index:                 break             i += 1             linked_list = linked_list.behind         if linked_list.behind is not None:             linked_list.behind.before = linked_list.before         if linked_list.before is not None:             linked_list.before.behind = linked_list.behind         linked_list.behind = None         linked_list.before = None         linked_list.value = None     def trave(linked_list):     if isinstance(linked_list, LinkedList):         print(linked_list)         if linked_list.behind is not None:             trave(linked_list.behind)     def find(linked_list, index):     if isinstance(linked_list, LinkedList):         i = 0         while linked_list.behind is not None:             if i == index:                 return linked_list             i += 1             linked_list = linked_list.behind         else:             if i < index:                 raise Exception(404)             return linked_list