2019.9.15单链表尾部添加和在指定位置添加节点的代码实现（接着之前完整版）

# coding:utf-8

class Node(object):
"""節點0"""
def __init__(self, elem):
self.elem = elem
self.next = None

# node = None(100)
class SingleLinkList(object):
"""單鏈表"""
def __init__(self, node=None):
self.__head = node

def is_empty(self):
"""鏈表是否爲空"""
return self.__head == None

def length(self):
"""鏈表長度"""
# cur遊樸，用來移動遍歷節點
cur = self.__head
# count記錄數量
count = 0
while cur != None:
count += 1
cur = cur.next
return count

def travel(self):
"""遍歷整個鏈表"""
cur = self.__head
while cur != None:
print(cur.elem, end=" ")
cur = cur.next
print("")

def add(self, item):
"""鏈表頭部添加元素，頭插法"""
node = Node(item)
node.next = self.__head
self.__head = node

def append(self, item):
"""鏈表尾部添加元素,尾插法"""
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 從0開始
"""
if pos <= 0:
self.add(item)
elif pos > (self.length()-1):
self.append(item)
else:

pre = self.__head
count = 0
while count < (pos-1):
count += 1
pre = pre.next
# 當循環退出後，pre指向pos-1位置
node = Node(item)
node.next = pre.next
pre.next = node

def remove(self, item):
"""刪除節點"""
pass

def search(self, item):
"""查找節點是否存在"""
pass

if __name__ == "__main__":
ll = SingleLinkList()
print(ll.is_empty())
print(ll.length())

ll.append(1)
print(ll.is_empty())
print(ll.length())

ll.append(2)
ll.add(8)
ll.append(3)
ll.append(4)
ll.append(5)
ll.append(6)
# 8 1 2 3 4 5 6
ll.insert(-1, 9) # 9 8 123456
ll.travel()
ll.insert(3, 100) # 9 8 1 100 2 3456
ll.travel()
ll.insert(10, 200) # 9 8 1 100 23456 200
ll.travel()