Python程式設計日記003 二叉樹專題

class

binarysearchtree
(object)
:    
def __init__
(self,key)
:        
self.key=key        
self.left=none       
self.right=none   
def find
(self,x)
:if x==self.key:
return self        
elif xreturn self.left.
find
(x)       
elif x>self.key and self.right:
return self.right.
find
(x)else
:return none         
def findmin
(self)
:if self.left:
return self.left.
findmin()
else
:return self    
def insert
(self,x)
:if xif self.left:                
self.left.
insert
(x)else
:                
tree=
binarysearchtree
(x)         
self.left=tree        
elif x>self.key:
if self.right:                
self.right.
insert
(x)else
:                
tree=
binarysearchtree
(x)  
self.right=tree 
def delete
(self,x)
:if self.
find
(x):
if xself.left=self.left.
delete
(x)return self            
elif x>self.key:   
self.right=self.right.
delete
(x)return self            
elif self.left and self.right:   
key=self.right.
findmin()
.key
self.key=key   
self.right=self.right.
delete
(key)
return self            
else
:if self.left:
return self.left    
else
:return self.right        
else
:return self

輸入某二叉樹的前序遍歷和中序遍歷的結果，請重建出該二叉樹。假設輸入的前序遍歷和中序遍歷的結果中都不含重複的數字。例如輸入前序遍歷序列和中序遍歷序列，則重建二叉樹並返回。

#class

treenode
:#    def __init__
(self, x)
:#        self.val = x
#        self.left = none
#        self.right = none
class
solution
:    # 返回構造的treenode根節點
def reconstructbinarytree
(self, pre, tin)
:        # write code here
if not pre or not tin:
return none
root=
treenode
(pre[0]
)        #rootval=pre[0]
p = self.
find
(pre[0]
,tin)
if p!=none:
root.left = self.
reconstructbinarytree
(pre[
1:p+1]
,tin[
0:p]
)            root.right = self.
reconstructbinarytree
(pre[p+1:
],tin[p+1:
])return root
def find
(self,val,tin)
:for j in
range
(len
(tin)):
if tin[j]
==val:
return j
return none

中序遍歷：左根右

後序遍歷：左右根

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