LeetCode106_从中序与后序遍历序列构造二叉树

1. 题目

给定两个整数数组 inorder 和 postorder ，其中 inorder 是二叉树的中序遍历， postorder 是同一棵树的后序遍历，请你构造并返回这颗 二叉树 。

提示:
1 <= inorder.length <= 3000
postorder.length == inorder.length
-3000 <= inorder[i], postorder[i] <= 3000      

2. 题解

from typing import List


class TreeNode:
    def __init__(self, val=0, left=None, right=None):
        self.val = val
        self.left = left
        self.right = right


class Solution:
    def buildTree(self, inorder: List[int], postorder: List[int]) -> TreeNode:
        if not inorder and not postorder:
            return None

        root_val = postorder[len(postorder) - 1]
        root = TreeNode(root_val)
        i = inorder.index(root_val)  # i = 1
        root.left = self.buildTree(inorder[: i], postorder[: i])
        root.right = self.buildTree(inorder[i + 1:], postorder[i: -1])
        return