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Python中的二叉树查找算法模块使用指南

python中的二叉树模块内容:

BinaryTree:非平衡二叉树
 AVLTree:平衡的AVL树
 RBTree:平衡的红黑树
以上是用python写的,相面的模块是用c写的,并且可以做为Cython的包。

FastBinaryTree
 FastAVLTree
 FastRBTree
特别需要说明的是:树往往要比python内置的dict类慢一些,但是它中的所有数据都是按照某个关键词进行排序的,故在某些情况下是必须使用的。

安装和使用

安装方法

安装环境:

ubuntu12.04, python 2.7.6

安装方法

下载源码,地址:https://bitbucket.org/mozman/bintrees/src
进入源码目录,看到setup.py文件,在该目录内运行   

python setup.py install

安装成功,ok!下面就看如何使用了。

应用

bintrees提供了丰富的API,涵盖了通常的多种应用。下面逐条说明其应用。

- 引用

如果按照一般模块的思路,输入下面的命令引入上述模块

> import bintrees

 
错了,这是错的,出现如下警告:(×××不可用,用×××)

  Warning: FastBinaryTree not available, using Python version BinaryTree.

  Warning: FastAVLTree not available, using Python version AVLTree.

  Warning: FastRBTree not available, using Python version RBTree.

正确的引入方式是:

  > from bintrees import BinaryTree   #只引入了BinartTree
  > from bintrees import *       #三个模块都引入了

- 实例化

看例子:

> btree = BinaryTree()
  > btree
  BinaryTree({})
  > type(btree)
  <class 'bintrees.bintree.BinaryTree'>

  
- 逐个增加键值对: .__setitem__(k,v) .复杂度O(log(n))(后续说明中,都会有复杂度标示,为了简单,直接标明:O(log(n)).)

看例子:

> btree.__setitem__("Tom","headmaster")
 > btree
 BinaryTree({'Tom': 'headmaster'})
 > btree.__setitem__("blog","http://blog.csdn.net/qiwsir")
 > btree
 BinaryTree({'Tom': 'headmaster', 'blog': 'http://blog.csdn.net/qiwsir'})

  
- 批量添加: .update(E)  E是dict/iterable,将E批量更新入btree. O(E*log(n))

看例子:

> adict = [(2,"phone"),(5,"tea"),(9,"scree"),(7,"computer")]
  > btree.update(adict)
  > btree
  BinaryTree({2: 'phone', 5: 'tea', 7: 'computer', 9: 'scree', 'Tom': 'headmaster', 'blog': 'http://blog.csdn.net/qiwsir'})

  
- 查找某个key是否存在: .__contains__(k)  如果含有键k,则返回True,否则返回False. O(log(n))

看例子:

> btree
 BinaryTree({2: 'phone', 5: 'tea', 7: 'computer', 9: 'scree', 'Tom': 'headmaster', 'blog': 'http://blog.csdn.net/qiwsir'})
 > btree.__contains__(5)
 True
 > btree.__contains__("blog")
 True
 > btree.__contains__("qiwsir")
 False
 > btree.__contains__(1)
 False

  
- 根据key删除某个key-value: .__delitem__(key), O(log(n))

看例子:

> btree
  BinaryTree({2: 'phone', 5: 'tea', 7: 'computer', 9: 'scree', 'Tom': 'headmaster', 'blog': 'http://blog.csdn.net/qiwsir'})
  > btree.__delitem__(5)    #删除key=5的key-value,即:5:'tea' 被删除.
  > btree
  BinaryTree({2: 'phone', 7: 'computer', 9: 'scree', 'Tom': 'headmaster', 'blog': 'http://blog.csdn.net/qiwsir'})

- 根据key值得到该kye的value: .__getitem__(key)

看例子:

> btree
 BinaryTree({2: 'phone', 7: 'computer', 9: 'scree', 'Tom': 'headmaster', 'blog': 'http://blog.csdn.net/qiwsir'})
 > btree.__getitem__("blog")
 'http://blog.csdn.net/qiwsir'
 > btree.__getitem__(7)
 'computer'
 > btree._getitem__(5)  #在btree中没有key=5,于是报错。
 Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
 AttributeError: 'BinaryTree' object has no attribute '_getitem__'

- 迭代器: .__iter__()

看例子:

> btree 
 BinaryTree({2: 'phone', 7: 'computer', 9: 'scree', 'Tom': 'headmaster', 'blog': 'http://blog.csdn.net/qiwsir'})
 > aiter = btree.__iter__()
 > aiter
 <generator object <genexpr> at 0xb7416dec>
 > aiter.next() #注意:next()一个之后,该值从list中删除
 2
 > aiter.next()
 7
 > list(aiter)
 [9, 'Tom', 'blog']
 > list(aiter)  #结果是空
 []
 > bool(aiter)  #but,is True
 True

- 树的数据长度: .__len__(),返回btree的长度。O(1)

看例子:

> btree
  BinaryTree({2: 'phone', 7: 'computer', 9: 'scree', 'Tom': 'headmaster', 'blog': 'http://blog.csdn.net/qiwsir'})
  > btree.__len__()
  5

- 找出key最大的k-v对: .__max__(),按照key排列,返回key最大的键值对。


- 找出key最小的键值对: .__min__()

看例子:

> btree
 BinaryTree({2: 'phone', 7: 'computer', 9: 'scree'})
 > btree.__max__()
 (9, 'scree')
 > btree.__min__()
 (2, 'phone')

- 两棵树的关系运算

看例子:

> other = [(3,'https://www.jb51.net'),(7,'qiwsir')]
 > bother = BinaryTree()  #再建一个树
 > bother.update(other) #加入数据

 > bother
 BinaryTree({3: 'https://www.jb51.net', 7: 'qiwsir'})
 > btree
 BinaryTree({2: 'phone', 7: 'computer', 9: 'scree'})
 
 > btree.__and__(bother)  #重叠部分部分
 BinaryTree({7: 'computer'})

 > btree.__or__(bother) #全部
 BinaryTree({2: 'phone', 3: 'https://www.jb51.net, 7: 'computer', 9: 'scree'})

 > btree.__sub__(bother)  #btree不与bother重叠的部分
 BinaryTree({2: 'phone', 9: 'scree'})
 
 > btree.__xor__(bother)  #两者非重叠部分
 BinaryTree({2: 'phone', 3: 'https://www.jb51.net, 9: 'scree'})

- 输出字符串模样,注意仅仅是输出的模样罢了: .__repr__()

看例子:

> btree
  BinaryTree({2: 'phone', 7: 'computer', 9: 'scree'})
  > btree.__repr__()
  "BinaryTree({2: 'phone', 7: 'computer', 9: 'scree'})"

- 清空树中的所有数据 :.clear(),O(log(n))

看例子:

> bother  
 BinaryTree({3: 'http://blog.csdn.net/qiwsir', 7: 'qiwsir'})
 > bother.clear()
 > bother
 BinaryTree({})
 > bool(bother)
 False

- 浅拷贝: .copy(),官方文档上说是浅拷贝,但是我做了操作实现,是下面所示,还不是很理解其“浅”的含义。O(n*log(n))

看例子:

> btree
 BinaryTree({2: 'phone', 7: 'computer', 9: 'scree'})
 > ctree = btree.copy()
 > ctree
 BinaryTree({2: 'phone', 7: 'computer', 9: 'scree'})

 > btree.__setitem__("github","qiwsir") #增加btree的数据
 > btree
 BinaryTree({2: 'phone', 7: 'computer', 9: 'scree', 'github': 'qiwsir'})
 > ctree
 BinaryTree({2: 'phone', 7: 'computer', 9: 'scree'}) #这是不是在说明属于深拷贝呢?
 
 > ctree.__delitem__(7) #删除ctree的一个数据
 > ctree
 BinaryTree({2: 'phone', 9: 'scree'})
 > btree
 BinaryTree({2: 'phone', 7: 'computer', 9: 'scree', 'github': 'qiwsir'})

  

- 移除树中的一个数据: .discard(key),这个功能与.__delitem__(key)类似.两者都不反悔值。O(log(n))

看例子:

> ctree
 BinaryTree({2: 'phone', 9: 'scree'})
 > ctree.discard(2) #删除后,不返回值,或者返回None
 > ctree
 BinaryTree({9: 'scree'})
 > ctree.discard(2) #如果删除的key不存在,也返回None
 > ctree.discard(3)
 > ctree.__delitem__(3) #但是,.__delitem__(key)则不同,如果key不存在,会报错。
 Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python2.7/site-packages/bintrees/abctree.py", line 264, in __delitem__
  self.remove(key)
  File "/usr/local/lib/python2.7/site-packages/bintrees/bintree.py", line 124, in remove
  raise KeyError(str(key))
  KeyError: '3'

- 根据key查找,并返回或返回备用值: .get(key[,d])。如果key在树中存在,则返回value,否则如果有d,则返回d值。O(log(n))

看例子:

> btree
 BinaryTree({2: 'phone', 7: 'computer', 9: 'scree', 'github': 'qiwsir'})
 > btree.get(2,"algorithm")
 'phone'
 > btree.get("python","algorithm") #没有key='python'的值,返回'algorithm'
 'algorithm'
 > btree.get("python") #如果不指定第二个参数,若查不到,则返回None
 >

- 判断树是否为空: is_empty().根据树数据的长度,如果数据长度为0,则为空。O(1)

看例子:

> ctree
 BinaryTree({9: 'scree'})
 > ctree.clear()  #清空数据
 > ctree
 BinaryTree({})
 > ctree.is_empty()
 True
 > btree
 BinaryTree({2: 'phone', 7: 'computer', 9: 'scree', 'github': 'qiwsir'})
 > btree.is_empty()
 False

- 根据key、value循环从树中取值:

.items([reverse])--按照(key,value)结构取值;

.keys([reverse])--key

.values([reverse])--value. O(n)

.iter_items(s,e[,reverse]--s,e是key的范围,也就是生成在某个范围内的key的迭代器 O(n)

看例子:

> btree
 BinaryTree({2: 'phone', 7: 'computer', 9: 'scree', 'github': 'qiwsir'})
 > for (k,v) in btree.items():
 ... print k,v
 ...
 2 phone
 7 computer
 9 scree
 github qiwsir
 > for k in btree.keys():
 ... print k
 ...
 2
 7
 9
 github
 > for v in btree.values():
 ... print v
 ...
 phone
 computer
 scree
 qiwsir
 > for (k,v) in btree.items(reverse=True): #反序
 ... print k,v
 ...
 github qiwsir
 9 scree
 7 computer
 2 phone

 > btree
 BinaryTree({2: 'phone', 5: None, 7: 'computer', 8: 'eight', 9: 'scree', 'github': 'qiwsir'})
 > for (k,v) in btree.iter_items(6,9): #要求迭代6<=key<9的键值对数据
 ... print k,v
 ...
 7 computer
 8 eight
 >

      

- 删除数据并返回该值:

.pop(key[,d]), 根据key删除树的数据,并返回该value,但是如果没有,并也指定了备选返回的d,则返回d,如果没有d,则报错;

.pop_item(),在树中随机选择(key,value)删除,并返回。

看例子:

> ctree = btree.copy()
 > ctree
 BinaryTree({2: 'phone', 7: 'computer', 9: 'scree', 'github': 'qiwsir'})

 > ctree.pop(2) #删除key=2的数据,返回其value
 'phone'
 > ctree.pop(2) #删除一个不存在的key,报错
 Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python2.7/site-packages/bintrees/abctree.py", line 350, in pop
  value = self.get_value(key)
  File "/usr/local/lib/python2.7/site-packages/bintrees/abctree.py", line 557, in get_value
  raise KeyError(str(key))
  KeyError: '2'
 
 > ctree.pop_item()  #随机返回一个(key,value),并已删除之
 (7, 'computer')
 > ctree
 BinaryTree({9: 'scree', 'github': 'qiwsir'})
 
 > ctree.pop(7,"sing") #如果没有,可以返回指定值
 'sing'

- 查找数据,并返回value: .set_default(key[,d]),在树的数据中查找key,如果存在,则返回该value。如果不存在,当指定了d,则将该(key,d)添加到树内;当不指定d的时候,添加(key,None). O(log(n))

看例子:

> btree
 BinaryTree({2: 'phone', 7: 'computer', 9: 'scree', 'github': 'qiwsir'})
 > btree.set_default(7) #存在则返回
 'computer'
 
 > btree.set_default(8,"eight") #不存在,则返回后备指定值,并加入到树
 'eight'
 > btree
 BinaryTree({2: 'phone', 7: 'computer', 8: 'eight', 9: 'scree', 'github': 'qiwsir'})
 
 > btree.set_default(5) #如果不指定值,则会加入None
 > btree
 BinaryTree({2: 'phone', 5: None, 7: 'computer', 8: 'eight', 9: 'scree', 'github': 'qiwsir'})

 > btree.get(2) #注意,.get(key)与.set_default(key[,d])的区别
 'phone'
 > btree.get(3,"mobile")  #不存在的 key,返回但不增加到树
 'mobile'
 > btree
 BinaryTree({2: 'phone', 7: 'computer', 8: 'eight', 9: 'scree', 'github': 'qiwsir'})

- 根据key删除值

.remove(key),删除(key,value)

.remove_items(keys),keys是一个key组成的list,逐个删除树中的对应数据

看例子:

> ctree
 BinaryTree({2: 'phone', 5: None, 7: 'computer', 8: 'eight', 9: 'scree', 'github': 'qiwsir'})
 > ctree.remove_items([5,6])  #key=6,不存在,报错
 Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python2.7/site-packages/bintrees/abctree.py", line 271, in remove_items
  self.remove(key)
  File "/usr/local/lib/python2.7/site-packages/bintrees/bintree.py", line 124, in remove
  raise KeyError(str(key))
  KeyError: '6'
 
 > ctree
 BinaryTree({2: 'phone', 7: 'computer', 8: 'eight', 9: 'scree', 'github': 'qiwsir'})
 > ctree.remove_items([2,7,'github']) #按照 列表中顺序逐个删除
 > ctree
 BinaryTree({8: 'eight', 9: 'scree'})

   
##以上只是入门的基本方法啦,还有更多内容,请移不到到文章开头的官方网站