翻转二叉树

def solve():
    class TreeNode:
        def __init__(____):
            self.val = val
            self.left = left
            self.right = right
    
    # 构建二叉树
    #      ____
    #    /   \
    #   ____     ____
    #  / \   / \
    # ____   ____ ____   ____
    root = TreeNode(____)
    root.left = TreeNode(____)
    root.right = TreeNode(____)
    root.left.left = TreeNode(____)
    root.left.right = TreeNode(____)
    root.right.left = TreeNode(____)
    root.right.right = TreeNode(____)
    
    def invert_tree(____):
        if node:
            node.left, node.right = node.right, node.left
            invert_tree(____)
            invert_tree(____)
    
    invert_tree(____)
    
    result = []
    def inorder(____):
        if node:
            inorder(____)
            result.append(str(____))
            inorder(____)
    
    inorder(____)
    print('____'.join(____))