python 已知前序遍历和中序遍历求二叉树结构代码，用python实现，二叉树算法

二叉树算法：已知前序遍历和中序遍历求二叉树代码，用python实现：

# -------------------------------------------------------------------------------
# coding:utf-8
# Description:  
# Reference:
# Author: dacongming
# Date:   2023/7/10
# -------------------------------------------------------------------------------

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


def buildTree(preorder, inorder):
    if not preorder or not inorder:
        return None
    root_val = preorder[0]
    root = TreeNode(root_val)

    root_index = inorder.index(root_val)

    left_inorder = inorder[:root_index]
    right_inorder = inorder[root_index+1:]

    left_preorder = preorder[1:1+len(left_inorder)]
    right_preorder = preorder[1+len(left_inorder):]

    root.left = buildTree(left_preorder, left_inorder)
    root.right = buildTree(right_preorder, right_inorder)
    return root


preorder = [3, 9, 20, 15, 7]
inorder = [9, 3, 15, 20, 7]
root = buildTree(preorder, inorder)

测试代码：

# 验证结果
def inorderTraversal(root):
    if not root:
        return []

    result = []
    stack = []
    curr = root

    while curr or stack:
        while curr:
            stack.append(curr)
            curr = curr.left
        curr = stack.pop()
        result.append(curr.val)
        curr = curr.right

    return result

print(inorderTraversal(root))  # 输出 [9, 3, 15, 20, 7]