python实现数据结构单链表

#python实现数据结构单链表
# -*- coding: utf-8 -*-


class Node(object):
    """节点"""
    
    def __init__(self, elem):
        self.elem = elem
        self.next = None  # 节点一开始初始化的时候并不知道下一个元素的地址，所以先设置为空


class SingLinkList(object):
    """单链表"""
    
    def __init__(self, node=None):
        self.__head = node
    
    def is_empty(self):
        """"判断是否为空"""
        return self.__head == None
    
    def length(self):
        """返回长度"""
        # cur游标用来移动遍历节点
        cur = self.__head
        # count 用来记录数量
        count = 0
        while cur != None:
            count += 1
            cur = cur.next
        return count
    
    def travel(self):
        """遍历链表"""
        # cur游标用来移动遍历节点
        cur = self.__head
        # count 用来记录数量
        count = 0
        while cur != None:
            print(cur.elem, end=' ')
            cur = cur.next
        print('
')
    
    def add(self, item):
        """"链表头部添加"""
        node = Node(item)
        node.next = self.__head  # 将新节点的next域指向首节点的头部
        self.__head = node
    
    def append(self, item):
        """链表尾部添加"""
        node = Node(item)
        if self.is_empty():
            self.__head = node
        else:
            cur = self.__head
            while cur.next != None:
                cur = cur.next
            cur.next = node
    
    def insert(self, pos, item):
        """
        指定位置添加元素
        :param pos: pos从0 开始
        :param item:
        :return:
        """
        if pos <= 0:
            self.add(item)
        elif pos > (self.length() - 1):
            self.append(item)
        else:
            pre = self.__head
            node = Node(item)
            count = 0
            while count < (pos - 1):
                count += 1
                pre = pre.next
            # 当循环退出后pre指向pos-1
            node.next = pre.next
            pre.next = node
    
    def remove(self, item):
        """删除节点"""
        pre = None
        cur = self.__head
        while cur != None:
            if cur.elem == item:
                # 判断次节点是不是头节点
                # 头结点：
                if cur == self.__head:
                    self.__head = cur.next
                else:
                    pre.next = cur.next
                break
            else:
                pre = cur
                cur = cur.next
    
    def search(self, item):
        """查找节点是否存在"""
        cur = self.__head
        while cur != None:
            if cur.elem == item:
                return True
            else:
                cur = cur.next
            return False


if __name__ == '__main__':
    l = SingLinkList()
    print(l.is_empty())
    l.add(0)
    l.append(1)
    l.add(8)
    print(l.length())
    l.append(2)
    l.append(2)
    l.append(4)
    l.travel()
    l.insert(-1, 7)
    l.insert(2, 1)
    l.travel()
    l.remove(8)
    l.travel()


# 后继节点：指的是下一个节点