Python实现二叉树

整体是基于链表思想做的。代码很简单，可阅读源码搞定。

class Node:
    def __init__(self,val,left_node=None,right_node=None):
        self._val=val
        self._left_node=left_node
        self._right_node=right_node
    
    @property
    def value(self):
        return self._val
    @value.setter
    def value(self,val):
        self._val=val
        
    @property
    def left(self):
        return self._left_node
    @left.setter 
    def left(self,left_node):
        self._left_node=left_node
        
    @property
    def right(self):
        return self._right_node
    @right.setter
    def right(self,right_node):
        self._right_node=right_node
        
        
class BinaryTree:
    def __init__(self,node):
        self._head=node
        
    def insert_left(self,node):
        if self._head.left:
            temp=self._head.left
            self._head.left=node
            node.left=temp
        else:
            self._head.left=node
    
    def insert_right(self,node):
        if self._head.right:
            temp=self._head.right
            self._head.right=node
            node.right=temp
        else:
            self._head.right=node
        
    def _get_left_child(self):
        return self._head.left

    def _get_right_child(self):
        return self._head.right
    
    def insert_left_child(self,node,is_left_ptr=False):
        ptr=self._get_left_child()
        if ptr:
            if is_left_ptr:
                ptr.left=node
            else:
                ptr.right=node
        else:
            self._head.left=node
 
    def insert_right_child(self,node,is_right_ptr=False):
        ptr=self._get_right_child()
        if ptr:
            if is_right_ptr:
                ptr.right=node
            else:
                ptr.left=node
        else:
            self._head.right=node
            

        
    def get_root_value(self):
        return self._head.value
    
    def get_left_value(self):
        return self._head.left.value
    
    def get_right_value(self):
        return self._head.right.value

    def get_root_ptr(self):
        return self._head

    def pre_order(self,root):
        if root is None:
            return 
        print(root.value,end=' ')
        self.pre_order(root.left)
        self.pre_order(root.right)
        
    def mid_order(self,root):
        if root is None:
            return
        self.mid_order(root.left)
        print(root.value,end=' ')
        self.mid_order(root.right)
        
    def bac_order(self,root):
        if root is None:
            return
        self.bac_order(root.left)
        self.bac_order(root.right)
        print(root.value,end=' ')

我们实现下图表示的二叉树，并使用前序、中序、后序遍历方法遍历。

测试：

# -*- coding: utf-8 -*-
from link_binary_tree import BinaryTree
from link_binary_tree import Node

a=BinaryTree(Node(1))
a.insert_left(Node(4))
a.insert_left_child(Node(8),True)
a.insert_left_child(Node(9))

a.insert_left(Node(2))
a.insert_left_child(Node(5))

a.insert_right(Node(3))
a.insert_right_child(Node(6),False)
a.insert_right_child(Node(7),True)

a.pre_order(a.get_root_ptr())
print()
a.mid_order(a.get_root_ptr())
print()
a.bac_order(a.get_root_ptr())

输出：

1 2 4 8 9 5 3 6 7 
8 4 9 2 5 1 6 3 7 
8 9 4 5 2 6 7 3 1 

总之，第一版代码，API设计的极其啰嗦和辣鸡。