2019.9.19-双向链表及添加元素代码

# coding:utf-8

class Node(object):
"""結點"""
def __init__(self, item):
self.elem = item
self.next = None
self.pre = None

class DoubuleLinkList(object):
"""雙向鏈表"""
# 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
node.next.prev = 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
node.prev = cur

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

def remove(self, item):
"""刪除節點"""
cur = self.__head
pre = None
while cur != None:
if cur.elem == item:
# 先判斷此結點是否是頭節點
# 頭節點
if cur == self.__head:
self.__head = cur.next
else:
pre.next = cur.next
break
else:
pre = cur
cur = cur.next

def search(self, item):
"""查找節點是否存在"""
cur = self.__head
while cur != None:
if cur.elem == item:
return True
else:
cur = cur.next
return False

if __name__ == "__main__":
dll = DoubuleLinkList()