单链表是内存地址不连续排列的线性表。单链表每个结点都有两个地址，第一个位置存储数据，第二个位置存储下个结点的内存地址。
class Node(object):
"""单链表结点"""
def __init__(self, val):
# _item 存储数据
self.val = val
# _next 是下一个结点的标识
self.next = None # 节点初始状态，不指向任何节点，置空
class SingleList(object):
"""单链表"""
def __init__(self, node=None):
self._head = node # 初始化，不指向任何结点
def is_empty(self):
if self._head is None:
return True
else:
return False
def length(self):
cur = self._head # 定义cur，指向第一个结点
count = 0
while cur is not None:
count += 1
cur = cur.next
return count
def travel(self):
cur = self._head # 定义cur，指向第一个结点
while cur is not None:
print(cur.val, end=" ")
cur = cur.next
print("")
def add(self, item):
"""链表头部添加元素，头插法"""
node = Node(item)
node.next = self._head # node指向首结点
self._head = node
def append(self, item):
node = Node(item)
if self.is_empty():
self._head = node
else:
cur = self._head
while cur.next is not None:
cur = cur.next
cur.next = node
def insert(self, pos, item):
"""
:param pos: 从0开始
:param item: 要添加的节点
:return:
"""
if pos <= 0:
self.add(item)
elif pos > self.length() - 1:
self.append(item)
else:
pre = self._head # 首节点
count = 0
while count < (pos - 1):
count += 1
pre = pre.next
node = Node(item)
node.next = pre.next
pre.next = node
def remove(self, item):
"""删除数据"""
cur = self._head
pre = None
while cur is not None:
if cur.val == item:
if cur == self._head: # 恰好是首节点
self._head = cur.next
else:
pre.next = cur.next
break
else:
pre = cur
cur = cur.next
def search(self, item):
cur = self._head
while cur is not None:
if cur.val == item:
return True
else:
cur = cur.next
return False
if __name__ == '__main__':
ll = SingleList()
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.insert(-1, 9)
ll.travel()
ll.insert(3, 100)
ll.travel()
ll.insert(10, 200)
ll.travel()
ll.remove(200)
ll.travel()
ll.remove(9)
ll.travel()
结果显示：
