# coding:utf-8
class node: 
    def __init__(self, value): 
        self.data = value 
        self.next = none
class linklist: 
    def __init__(self, data=[0]): 
        self.head = none 
        self.init_link_list(data)
# 初始化链表 
    # data 为数组 
    def init_link_list(self, data): 
        if len(data) == 0: 
            print(initialization data is null) 
            return 
        self.head = node(data[0]) 
        current = self.head 
        for index in data[1:]: 
            current.next = node(index) 
            current = current.next
# 获取当前结点 
    def get_node(self, index): 
        if self.is_empty(): 
            print(link is empty) 
            return 
        if index > self.get_length() or index <= 0:
print("node is not exist")
return
current = self.head
i = 0
while i < index:
if i == index - 1:
return current
current = current.next
i += 1
# 获取当前元素的值
def get_data(self, index):
current = self.get_node(index)
if current is none:
return "node is not exist"
return current.data
# 打印链表
def print_link(self):
if self.is_empty():
return
list = []
current = self.head
while current.next is not none:
list.append(current.data)
current = current.next
else:
list.append(current.data)
print(list)
# 获取链表长度
def get_length(self):
if self.is_empty():
return 0
current = self.head
count = 0
while current.next is not none:
count += 1
current = current.next
else:
count += 1
return count
# 判断链表是否为空
# 如果为空，返回true
# 如果不为空，返回false
def is_empty(self):
return self.head is none
# 当前元素之后插入一个元素
# index 元素索引
# data 插入的值
def add_after(self, index, data):
current = self.get_node(index)
if current is none:
return "node is not exist"
current_next = current.next
current.next = node(data)
current = current.next
current.next = current_next
# 在当前元素之前插入一个元素
def add_before(self, index, data):
if index == 1:
current = self.get_node(index)
self.head = node(data)
self.head.next = current
return
pre = self.get_pre_node(index)
current = pre.next
pre.next = node(data)
pre = pre.next
pre.next = current
# 获取当前元素的前一个元素
def get_pre_node(self, index):
if self.is_empty():
print("link is empty")
return
if index > self.get_length() or index <= 1: 
            print(node is not exist) 
            return 
        pre = self.head 
        i = 0 
        while i < index: 
            if i == index - 2: 
                return pre 
            pre = pre.next 
            i += 1
# 删除指定元素，并返回删除元素的值 
    def remove(self, index): 
        if index == 1 and not self.is_empty(): 
            data = self.head.data 
            self.head = self.head.next 
            return data 
        pre_node = self.get_pre_node(index) 
        current = self.get_node(index) 
        if pre_node is none or current is none: 
            print(data is not exist) 
        pre_node.next = current.next 
        return current.data
# 修改当前结点的值 
    def update(self, index, data): 
        current = self.get_node(index) 
        if current is none: 
            return current node is none 
        current.data = data
# 将新链表合并到当前链表 
    def merge(self, data): 
        size = self.get_length() 
        last_node = self.get_node(size) 
        last_node.next = data.head 
        return self
# test 
y = (1,2,3,4) 
s = [a, b, c, d] 
linklist = linklist(y) 
# linklist.init_link_list([a, b, c, d]) 
# second = linklist() 
# second.init_link_list([x, y, z]) 
# linklist.add_after(-1, x) 
# linklist.add_after(1, y) 
# linklist.init_link_list([]) 
# linklist.add_before(1,x) 
# linklist.print_link() 
# print(item:, linklist.get_data(2)) 
# print(length:, linklist.get_length()) 
# print(is empty, linklist.is_empty()) 
# print(linklist.get_pre_node(3).data) 
# print(remove node:,linklist.remove(2)) 
# linklist.merge(second)
linklist.print_link()