python实现跳表SkipList的示例代码

class Node():
  def __init__(self,key,value,level):
'''
:param level:每个node对应的nexts层数不同
'''
self.key=key
self.value=value
self.nexts=[None]*level#节点类型next指针，初始值为空
  def __str__(self):
#return "[key:"+str(self.key)+", value:"+str(self.value)+" len:"+str(len(self.nexts))+"]"
return "["+str(self.key)+","+str(self.value)+","+str(len(self.nexts))+"]"

'''
跳表 Skip List ，其初衷是为了替代红黑树
'''
import random
import mkl_random
import time
class SkipList():
 def __init__(self):
  #头节点不存储任何数据
  self.MAX_LEVEL = 32  # 最大level层数
  self.__first=SkipList.Node(None, None, self.MAX_LEVEL)#头节点
  self.__level=0#实际的level层数
  self.__size=0#Jiedian个数
  self.__p=0.25#用于生成添加节点时的随机level
  return
 class Node():
  def __init__(self,key,value,level):
'''
:param level:每个node对应的nexts层数不同
'''
self.key=key
self.value=value
self.nexts=[None]*level
  def __str__(self):
#return "[key:"+str(self.key)+", value:"+str(self.value)+" len:"+str(len(self.nexts))+"]"
return "["+str(self.key)+","+str(self.value)+","+str(len(self.nexts))+"]"
 def get(self,key):
  '''
  :param key:
  :return: key对应的value
  '''
  self.keyCheck(key)
  node=self.__first
  for level in range(self.__level - 1,-1,-1):
#在该层查找，key大于节点的key向前查找
while node.nexts[level] and node.nexts[level].key<key:
 node=node.nexts[level]
if node.nexts[level] and node.nexts[level].key==key:#相等则找到，否则向下寻找
 return node.nexts[level].value
  return None
 def put(self,key,value):
  '''
  return:原来的value，原来不存在key则为空
  '''
  self.keyCheck(key)
  prev=[None]*self.__level
  node=self.__first
  for i in range(self.__level - 1, -1, -1):
while node.nexts[i] and node.nexts[i].key<key:
 node=node.nexts[i]
if node.nexts[i] and node.nexts[i].key==key:
 oldValue=node.nexts[i].value
 node.nexts[i].value=value
 return oldValue
prev[i]=node#保存当前level小于key的node
  newLevel=self.randomLevel()
  newNode=SkipList.Node(key,value,newLevel)
  for i in range(newLevel):
if i<self.__level:
 newNode.nexts[i]=prev[i].nexts[i]
 prev[i].nexts[i]=newNode
else:
 self.__first.nexts[i]=newNode
  self.__size+=1
  self.__level=max(self.__level, newLevel)
  return None
 def remove(self,key):
  '''
  :return: 节点对应的value值，不存在则返回None
  '''
  self.keyCheck(key)
  prev=[None]*self.__level
  node=self.__first
  flag=False#该节点是否被查找到
  for i in range(self.__level - 1, -1, -1):
while node.nexts[i] and node.nexts[i].key<key:
 node=node.nexts[i]
if node.nexts[i].key==key:
 flag=True
prev[i]=node
  if not flag:
return None
  removedNode=node.nexts[0]#需要被删除的节点
  for i in range(len(removedNode.nexts)):#该nexts一定小于等于prev的长度
prev[i].next[i]=removedNode.nexts[i]
  self.__size-=1
  newLevel=self.__level
  while newLevel>0 and not self.__first.nexts[newLevel - 1]:
newLevel-=1
  self.__level=newLevel
  return removedNode.value
 def keyCheck(self, key):
  '''
  限制传入key不能为空
  '''
  if key!=0 and not key:
raise AttributeError("key can not be None")
 def size(self):
  return self.__size
 def isEmpty(self):
  return self.__size == 0
 def randomLevel(self):#生成一个随机的层数
  level=1
  while mkl_random.rand()<self.__p and level<self.MAX_LEVEL:
level+=1
  return level
 def __str__(self):
  result=""
  for i in range(self.__level - 1, -1, -1):
result+=str(i)
node = self.__first
while node.nexts[i]:
 result+=str(node.nexts[i])
 node=node.nexts[i]
result+='\n'
  print("level:"+str(self.__level))
  return result
 def showFirst(self):
  for item in self.__first.nexts:
print(item,end=' ')
  print()
def timeCalculate(container, size:int):
 begin=time.time()
 for i in range(size):
  if isinstance(container,dict):
container[i]= i * 3
  else:
container.put(i, i * 3)
 error_count = 0
 for i in range(size):
  if container.get(i) != i * 3:
#print("wrong " + str(i) + ":" + str(skipList.get(i)))
error_count+=1
 end=time.time()
 print(type(container))
 print(f'error rate:{float(error_count) / size:0.5f}')
 print(f'time cost:{float(end-begin)*1000:0.3f} ms')

if __name__=='__main__':
 timeCalculate({},1000000)
 timeCalculate(SkipList(),10000)