编写二叉树的remove()函数

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

def remove(root, key):
    if root is None:
        return root
    
    if key < root.val:
        root.left = remove(root.left, key)
    elif key > root.val:
        root.right = remove(root.right, key)
    else:
        if root.left is None:
            return root.right
        elif root.right is None:
            return root.left
        else:
            successor = find_successor(root.right)
            root.val = successor.val
            root.right = remove(root.right, successor.val)
    
    return root

def find_successor(node):
    while node.left is not None:
        node = node.left
    return node

# 示例用法
root = TreeNode(5)
root.left = TreeNode(3)
root.right = TreeNode(7)
root.left.left = TreeNode(2)
root.left.right = TreeNode(4)
root.right.left = TreeNode(6)
root.right.right = TreeNode(8)

print("原始二叉树：")
# 输出原始二叉树

key = 3
root = remove(root, key)

print("删除节点 {} 后的二叉树：")
# 输出删除节点后的二叉树