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leetcode_construct binary tree from inorder and postorder traversal

admin 11月 13, 2020 0

Construct Binary Tree from Inorder and Postorder Traversal

Given inorder and postorder traversal of a tree, construct the binary tree.
（根据中序遍历和后序遍历构建二叉树）

Example:

1. 递归

递归构建二叉树，首先根据后序遍历确定根节点，在根据中序遍历定位到根节点。其中，中序遍历根节点左边的为左子树，右边的为右子树。具体实现过程如下：


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

class :
    def buildTree(self, inorder: List[int], postorder: List[int]) -> TreeNode:
        if not inorder:
            return None
        
        root = TreeNode(postorder[-1])
        index = inorder.index(postorder[-1])
        
        root.left = self.buildTree(inorder[:index], postorder[:index])
        root.right = self.buildTree(inorder[index+1:], postorder[index:-1])
        
        return root