二叉树递归遍历的python实现

一、节点类的定义

class Node(): 
    def __init__(self, data, left, right):                                       
        self.data = data                                                            
        self.left = left                                                            
        self.right = right

二、生成二叉树

class BTree:                                                                        
    def __init__(self):                                                             
        self.root = None                                                                                                                  

    def insert(self, data):   #插入节点                                                   
        r = self.root                                                            
        if r is None:                                                            
            self.root = Node(data, None, None)                                  
            return                                                                  
        while True:                                                                 
            # 比根结点小放在左边                                                    
            if r.data > data:                                                       
                if r.left is None:                                                  
                    r.left = Node(data, None, None)                             
                    break                                                           
                else:                                                               
                    r = r.left                                                      
            else:                                                                   
                # 比根结点大放在右边                                                
                if r.right is None:                                                 
                    r.right = Node(data, None, None)                            
                    break                                                           
                else:                                                               
                    r = r.right         

三、前序遍历

def preoder(self, root):                                                      
        if root is None:                                                            
            return                                                                  
        else:                                                                                                                                  
            print root.data                                                        
            self.preoder(root.left)                          
            self.preoder(root.right)       

四、中序遍历

def midoder(self, root):                                                      
        if root is None:                                                            
            return                                                                  
        else:                                                                                                                                                                                          
            self.midoder(root.left) 
            print root.data                         
            self.midoder(root.right)  

五、后序遍历

def postoder(self, root):                                                      
        if root is None:                                                            
            return                                                                  
        else:                                                                                                                                                                                          
            self.postoder(root.left)                        
            self.postoder(root.right) 
            print root.data  

六、测试

if __name__ == '__main__':                                                          
    bt = BTree()
    L=[3,7,5,8,9,10,11,2,6,4]
    for i in L:                                      
      bt.insert(i)                                                                                                                       
    bt.preoder(bt.root)  
    bt.midoder(bt.root) 
    bt.postoder(bt.root)                                                       

七、总代吗

class Node():
    def __init__(self,root):
        self.root=root
        self.lchild=None
        self.rchild=None

class Bitree():
    def __init__(self):
        self.root=None

    def insert(self,root,node):         #插入节点
        if root:
            if root.root>node.root:
                if root.lchild:
                    self.insert(root.lchild,node)
                else:
                    root.lchild=node
            else:
                 if root.rchild:
                     self.insert(root.rchild,node)
                 else:
                     root.rchild=node
        else:
          return 0

    def initBitree(self,data):        #生成二叉树
        root=Node(data[0])
        length=len(data)
        for x in range(1,length):
            node=Node(data[x])
            self.insert(root,node)
        return root


    def preoder(self,root):       #先序遍历
      if root:
        print(root.root)
        self.preoder(root.lchild)
        self.preoder(root.rchild)

    def midoder(self,root):      #中序遍历
        if root:
            self.midoder(root.lchild)
            print(root.root)
            self.midoder(root.rchild)

    def postoder(self,root):      #后序遍历
        if root:
            self.postoder(root.lchild)
            self.postoder(root.rchild)
            print(root.root)




if __name__ == '__main__':
    data=[3,7,5,8,9,10,11,2,6,4]
    Bitree=Bitree()
    a=Bitree.initBitree(data)
    print('前序遍历:')
    Bitree.preoder(a)
    print('中序遍历:')
    Bitree.midoder(a)
    print('后序遍历:')
    Bitree.postoder(a)