链表
链表(Linked list)是⼀种常⻅的基础数据结构,是⼀种线性表,但是不像顺序表⼀样连续存储数据,⽽是在每⼀个节点(数据存储单元)⾥存放下⼀个节点的位置信息(即地址)。
单向循环链表
单链表的⼀个变形是单向循环链表,链表中最后⼀个节点的next域不再为None,⽽是指向链表的头节点。
语法实现:
class Node(object):
"""结点类"""
def __init__(self, item):
self.item = item
self.next = None
class CyclesSingleLinkList():
"""单向循环链表"""
def __init__(self, node=None):
self.__head = node
def is_empty(self):
"""链表是否为空
:return 如果链表为空 返回真
"""
return self.__head is None
def length(self):
"""链表长度"""
# 如果是空链表
if self.is_empty():
return 0
cur = self.__head
count = 1
while cur.next != self.__head:
count += 1
cur = cur.next
return count
def travel(self):
"""遍历整个链表"""
if self.is_empty():
print("")
return
cur = self.__head
while cur.next != self.__head:
print(cur.item, end=" ")
cur = cur.next
# 从循环退出,cur指向的是尾结点
print(cur.item)
def add(self, item):
"""链表头部添加元素
:param item: 要保存的具体数据
"""
node = Node(item)
if self.is_empty():
self.__head = node
node.next = node
# 寻找尾结点
cur = self.__head
while cur.next != self.__head:
cur = cur.next
# 从循环中退出,cur指向尾结点
node.next = self.__head
self.__head = node
cur.next = self.__head
def append(self, item):
"""链表尾部添加元素"""
node = Node(item)
#如果列表为空,直接添加结点
if self.is_empty():
self.__head = node
node.next = node
else:
cur = self.__head
while cur.next != self.__head:
cur = cur.next
#退出循环的时候,cur指向尾结点
cur.next = node
node.next = self.__head
def insert(self, pos, item):
"""指定位置添加元素"""
# 在头部添加元素
if pos <= 0:
self.add(item)
# 在尾部添加元素
elif pos >= self.length():
self.append(item)
else:
cur = self.__head
count = 0
while count < (pos - 1):
count += 1
cur = cur.next
# 退出循环的时候,cur指向pos前一个位置
# node插入到pos位置前
node = Node(item)
node.next = cur.next
cur.next = node
def remove(self,item):
"""删除结点"""
if self.is_empty():
return
# 当前游标
cur = self.__head
# 当前游标的上一个游标
pre = None
while cur.next != self.__head:
# 找到了要删除的元素
if cur.item == item:
# 在头部找到了元素
if cur == self.__head:
# 先找到尾结点
rear = self.__head
while rear.next != self.__head:
rear = rear.next
# 退出循环后,rear指向尾结点
self.__head = cur.next
rear.next = self.__head
else:
# 在中间位置找到了元素
pre.next = cur.next
return
# 不是要找的元素,移动游标
pre = cur
cur = cur.next
# 退出循环后,cur指向尾结点
if cur.item == item:
# 链表只有一个节点
if cur == self.__head:
self.__head = None
else:
pre.next = self.__head
def search(self,item):
"""查找结点是否存在"""
if self.is_empty():
return False
cur = self.__head
while cur.next != self.__head:
if cur.item == item:
return True
cur = cur.next
# 退出循环后,cur指向为尾结点
if cur.item == item:
return True
return False
if __name__ == '__main__':
ll = CyclesSingleLinkList()
print(ll.length())
ll.travel()
ll.append(1)
print(ll.length()) #1
ll.travel() #1
ll.add(2)
print(ll.length()) #2
ll.travel()#2 1
ll.insert(1,3)
ll.travel() #2 3 1
ll.remove(1)
ll.travel() #2 3