106.从中序与后序遍历序列构造二叉树.py

#
# @lc app=leetcode.cn id=106 lang=python3
#
# [106] 从中序与后序遍历序列构造二叉树
#

# @lc code=start
# Definition for a binary tree node.
# 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]) -> Optional[TreeNode]:
        if not inorder or not postorder:
            return
        
        root=TreeNode(postorder[-1])
        idx=inorder.index(root.val)

        root.left=self.buildTree(inorder[:idx],postorder[:idx])
        root.right=self.buildTree(inorder[idx+1:],postorder[idx:-1])

        return root
# @lc code=end