函數說明：
雙鏈表的相關操作：
- 初始化；
- 判空；
- 求長度；
- 插入節點：頭插、尾插、隨機插入；
- 刪除節點；
- 遍歷節點；
- 查找節點（搜索節點）；
代碼：
class Node(object):
def __init__(self, elem):
self.elem = elem
self.prev = None
self.next = None
class DoubleLinkList(object):
"""雙向循環鏈表"""
def __init__(self, node = None): # 和單鏈表一致
self.__head = node
def is_empty(self): # 和單鏈表一致
"""鏈表是否爲空"""
return self.__head is None
def length(self): # 和單鏈表一致
# 遊標用來遍歷節點
cur = self.__head
# 節點計數器，初始值影響while循環的判斷條件
counter = 0
while cur != None :
counter += 1
cur = cur.next
return counter
def travel(self): # 和單鏈表一致
cur = self.__head
while cur != None:
print(cur.elem)
cur = cur.next
def add(self, item):
"""鏈表頭部添加元素"""
# print("=====頭插法=====")
node = Node(item)
# 以下代碼的順序不唯一
node.next = self.__head
self.__head = node
node.next.prev = node
def append(self, item):
"""鏈表尾部添加元素"""
node = Node(item)
# print("=====尾插法=====")
# 特殊情況
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
@pos: 從0開始 例：insert(2,100)
"""
if pos <= 0 :
self.add(item)
elif pos > (self.length() - 1):
self.append(item)
else:
node = Node(item)
cur = self.__head
count = 0
while count < pos:
cur = cur.next
count += 1
# 當循環退出後，cur指向pos位置
node.next = cur
node.prev = cur.prev
cur.prev.next = node
cur.prev = node
def search(self, item): # 和單鏈表一致
"""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
# 難度係數高
def remove(self, item):
cur = self.__head
while cur != None:
if cur.elem == item:
# 判斷此節點是否爲頭節點
if cur == self.__head:
self.__head = cur.next
if cur.next:
# 鏈表是否只有一個節點
cur.next.prev = None
else:
cur.prev.next = cur.next
if cur.next:
# 不是尾節點
cur.next.prev = cur.prev
break
# pass
else:
cur = cur.next