Python BTree 学习－广度优先搜索
不说别的见源码
#coding=utf-8
import sys, os
import bisect
import string
class Entity(object):
"""data entity"""
__slots__ = ("key", "value",)
def __init__(self, key, value):
self.key = key
self.value = value
def __str__(self):
return self.key
def __unicode__(self):
return self.__str__()
def __cmp__(self, key):
if key > self.key:
return 1
elif key == self.key:
return 0
else:
return -1
class Node(object):
"""B Node"""
#__slots__ = ("parent", "entities", "childes",)
def __init__(self):
self.parent = None
self.entities = []
self.childes = []
def find(self, key):
i = bisect.bisect_left(self.entities, key)
if i != len(self.entities) and self.entities[i].key == key:
return self.entities[i].value
def delete(self, key):
"""delete key"""
i = bisect.bisect_left(self.entities, key)
if i != len(self.entities) and self.entities[i].key == key:
e = self.entities[i]
del self.entities[i]
return i, e
else:
return None, None
def is_leaf(self):
return len(self.childes) == 0
def add_entity(self, entity):
self.entities.append(entity)
self.entities.sort(key=lambda x:x.key)
def add_child(self, node):
self.childes.append(node)
node.parent = self
self.childes.sort(key=lambda x:x.entities[0].key)
class BTree(object):
def __init__(self, size=6):
self.size = size
self.root = None
self.length = 0
def add(self, key, value=None):
self.length += 1
if self.root:
current = self.root
while not current.is_leaf():
for i, e in enumerate(current.entities):
if e.key > key:
current = current.childes[i]
break
elif e.key == key:
e.value = value
return
else:
current = current.childes[-1]
current.add_entity(Entity(key, value))
if len(current.entities) > self.size:
self._split_(current)
else:
#init root
self.root = Node()
self.root.add_entity(Entity(key, value))
def _split_(self, node):
"""Rules
1、middle index node become parent
2、create right Nodes move parents right go to this node
"""
middle = len(node.entities) / 2
top = node.entities[middle]
right = Node()
for e in node.entities[middle + 1:]:
right.add_entity(e)
for n in node.childes[middle + 1:]:
right.add_child(n)
left = node
left.entities = node.entities[:middle]
left.childes = node.childes[:middle + 1]
parent = node.parent
if parent:
parent.add_child(right)
parent.add_entity(top)
if len(parent.entities) > self.size:
self._split_(parent)
else:
self.root = Node()
self.root.add_entity(top)
self.root.add_child(left)
self.root.add_child(right)
def get(self, key):
e, v = self._find_node_(key)
return v
def _find_node_(self, key):
if self.root:
current = self.root
while current.entities:
bisect.bisect_left(current.entities, key)
for i, e in enumerate(current.entities):
if e.key > key:
current = current.childes[i]
break
elif e.key == key:
return e, e.value
else:
current = current.childes[-1]
def delete(self, key):
"""#一般都标记删除不真删除"""
pass
def bfs(root):
"""Iterator traverses a tree in breadth-first order."""
queue = []
queue.append(root)
while len(queue) > 0:
node = queue.pop(0)
yield node
for child in node.childes:
queue.append(child)
return
if __name__ == '__main__':
t = BTree()
for i in xrange(26):
key = string.lowercase[i % 26]
value = i
t.add(key, value)
root = t.root
print "generate tree ......"
for node in bfs(root):
if node.parent:
print "parent",
for e in node.parent.entities:
print e,
print
for e in node.entities:
print e,
print
print
print "test btree get"
for i in xrange(26):
key = string.lowercase[i % 26]
print key, t.get(key), "-",