⽤python实现⼀个跳跃表
# coding: utf-8
import random
class Node(object):
"""
跳跃表节点
"""
def__init__(self, key, level):
self.key = key
# 当前节点的指向的下⼀个节点, ⽤列表维护对应的层数, 列表的索引是层数, 对象是节点
self.forward =[None]*(level +1)
def__str__(self):
return"Node({})".format(str(self.key))
class SkipList(object):
"""
跳跃表
"""
def__init__(self, max_lvl, P):
self.max_level = max_lvl  # 最⾼层数
self.P = P  # 掷硬币的建层概率
self.header = Node(-1, self.max_level)# 初始化头节点
self.level =0# 当前层数
def random_level(self):
lvl =0
while random.random()< self.P and lvl < self.max_level:
lvl +=1
return lvl
def insertElement(self, key):
update =[None]*(self.max_level +1)
current = self.header
"""
从跳越列表的最⾼层开始向后移动当前引⽤
当要插⼊的键⼤于当前节点旁边的键值时，向后移动当前引⽤
否则在 update 中插⼊当前值，向下移动⼀层并继续搜索
"""
for i in range(self.level,-1,-1):
while current.forward[i]and current.forward[i].key < key:
current = current.forward[i]# 往右挪
update[i]= current
current = current.forward[0]
"""
如果 current 是 NULL 意味着我们已经到达了列表尾部或当前节点和要插⼊的节点值不⼀样, 我们要在 update[0] 和 current 之间插⼊        """
if current is None or current.key != key:
# 为节点随机⽣成层数
rlevel = self.random_level()
# 如果超过当前层, 补全中间层
if rlevel > self.level:
for i in range(self.level +1, rlevel +1):
for i in range(self.level +1, rlevel +1):
update[i]= self.header
# 更新当前跳跃表的层数
self.level = rlevel
# ⽣成新的节点
n = Node(key, rlevel)
# 插⼊每⼀层
for i in range(rlevel +1):
n.forward[i]= update[i].forward[i]
update[i].forward[i]= n
# print("Successfully inserted key {}".format(key))
def delete_element(self, search_key):
update =[None]*(self.max_level +1)
current = self.header
for i in range(self.level,-1,-1):
while current.forward[i]and current.forward[i].key < search_key:                current = current.forward[i]
update[i]= current
current = current.forward[0]
if current is not None and current.key == search_key:
for i in range(self.level +1):
# 如果往上层没有要删除的节点则提前结束
if update[i].forward[i]!= current:
break
update[i].forward[i]= current.forward[i]
del current
while self.level >0and self.header.forward[self.level]is None:                self.level -=1
print("Successfully deleted {}".format(search_key))
def search_element(self, key):
current = self.header
n =0
for i in range(self.level,-1,-1):
while current.forward[i]and current.forward[i].key < key:
current = current.forward[i]
n +=1
print(n,"次")
random pythoncurrent = current.forward[0]
if current and current.key == key:
# print("Found key ", key)
pass
def display_list(self):
print("*****Skip List******")
head = self.header
for lvl in range(self.level +1):
print("Level {}: ".format(lvl))
node = head.forward[lvl]
node_list =[]
while node is not None:
while node is not None:
node_list.append(str(node.key))
node = node.forward[lvl]
print("->".join(node_list))
if __name__ =='__main__':
lst = SkipList(5,0.5)
lst.insertElement(3)
lst.insertElement(7)
lst.insertElement(12)
lst.insertElement(6)
lst.insertElement(19)
lst.insertElement(9)
lst.insertElement(26)
lst.insertElement(21)
lst.insertElement(17)
lst.insertElement(25)
lst.display_list()
lst.search_element(12)
lst.delete_element(12)
lst.display_list()
# print("*" * 20)
# print(lst.header)
# print(lst.header.forward[0])
# print(lst.header.forward[0].forward[0])
# print(lst.header.forward[0].forward[0].forward[0]) #
# print("*" * 20)
# print(lst.header.forward[2])
# print(lst.header.forward[2].forward[2])
# print(lst.header.forward[2].forward[2].forward[2])

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