使用前序中序求后序遍历，使用中序后序求前序遍历--Python

本文链接：https://blog.youkuaiyun.com/weixin_41287060/article/details/99400963

使用前序中序求后序遍历

# encoding: utf-8
class TreeNode:
    def __init__(self, x):
        self.val = x
        self.left = None
        self.right = None
class Solution:
    # 返回构造的TreeNode根节点
    def reConstructBinaryTree(self, pre, tin):
        if len(pre)==0:
            return None
        root=TreeNode(pre[0])
        TinIndex=tin.index(pre[0])
        root.left=self.reConstructBinaryTree(pre[1:TinIndex+1], tin[0:TinIndex])
        root.right=self.reConstructBinaryTree(pre[TinIndex+1:], tin[TinIndex+1:])
        return root
    def PostTraversal(self,root):  #后序遍历
        if root != None:
            self.PostTraversal(root.left)
            self.PostTraversal(root.right)
            print(root.val)
pre=[1,2,4,7,3,5,6,8]
tin=[4,7,2,1,5,3,8,6]
S=Solution()
root=S.reConstructBinaryTree(pre,tin)
S.PostTraversal(root)

根据上述代码修改–使用中序后序求前序遍历

class TreeNode:
    def __init__(self,x):
        self.val=x
        self.left=None
        self.right=None

class Solution:
    def reConstructBinaryTree(self,post,tin):
        if len(post)==0:
            return None
        root=TreeNode(post[-1])
        TinIndex=tin.index(post[-1])
        root.left=self.reConstructBinaryTree(post[0:TinIndex],tin[0:TinIndex])
        root.right=self.reConstructBinaryTree(post[TinIndex:len(post)-1],tin[TinIndex+1:])
        return root
    
    def PreTraversal(self,root):
        if root !=None:
            print(root.val)
            self.PreTraversal(root.left)
            self.PreTraversal(root.right)

post =[7,4,2,5,8,6,3,1]
tin  =[4,7,2,1,5,3,8,6]
pre  =[1,2,4,7,3,5,6,8]

S=Solution()
root=S.reConstructBinaryTree(post,tin)
S.PreTraversal(root)