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。
实现:
class Node(object):
"""节点"""
def __init__(self, elem):
self.elem = elem
self.next = None
class SingleLinkList(object):
"""单向链表"""
def __init__(self, node=None):
self.__head = node
def is_empty(self):
return self.__head == None
def length(self):
"""链表长度"""
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.__head == None:
return
cur = self.__head
while cur.next != self.__head:
print(cur.elem, end=" ")
cur = cur.next
# 退出循环,cur指向尾节点,但尾节点的元素未打印
print(cur.elem)
def add(self, item):
"""链表头部添加元素"""
node = Node(item)
if self.is_empty(): # 链表为空的时候
self.__head = node # 设置当前节点为头节点
node.next = node # 并将该节点的next指向自己
else:
cur = self.__head
while cur.next != self.__head:
cur = cur.next
# 退出循环 cur 指向尾部节点
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)
if self.is_empty():
self.__head = node
node.next = self.__head
else:
cur = self.__head
while cur.next != self.__head:
cur = cur.next
node.next = self.__head
cur.next = node
def insert(self, pos, item):
"""
指定位置添加元素
:param pos: pos 从哪里开始
:param item:
:return:
"""
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
# 当循环退出后,pre指向pos-1的位置
node = Node(item)
node.next = pre.next
pre.next = node
def remove(self, item):
"""删除节点"""
if self.is_empty():
return
cur = self.__head
pre = None
while cur.next != self.__head:
if cur.elem == item:
# 判断是否为头节点
if cur == self.__head:
# 找到尾部节点
rear = self.__head
while rear.next != self.__head:
rear = rear.next
self.__head = cur.next
rear.next = self.__head
else:
pre.next = cur.next # 什么意思哟 斩断中间的,上一个指向当前斩断的下一个元素
return
else:
pre = cur
cur =cur.next
# 退出循环, cur 指向尾节点
if cur.elem == item :
if cur == self.__head:
# 说明就只有一个节点
self.__head = None
else:
pre.next = self.__head
def search(self, item):
cur = self.__head
while cur.next != self.__head:
if cur.elem == item:
return True
else:
cur = cur.next
# 退出循环,cur指向尾节点
if cur.elem == item:
return True
return False
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)
ll.travel()
ll.insert(-1, 9) # 9 8 1 23456
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()
ll.remove(100)
ll.travel()
ll.remove(9)
ll.travel()
ll.remove(200)
ll.travel()
print(ll.search(77))