二进制搜索树删除节点函数不删除

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

def deleteNode(root, key):
    if not root:
        return root
    
    # 找到要删除的节点
    if key < root.val:
        root.left = deleteNode(root.left, key)
    elif key > root.val:
        root.right = deleteNode(root.right, key)
    else:
        # 没有子节点或只有一个子节点的情况
        if not root.left:
            return root.right
        elif not root.right:
            return root.left
        
        # 有两个子节点的情况，找到后继节点
        successor = root.right
        while successor.left:
            successor = successor.left
        
        # 将后继节点的值复制到要删除的节点中
        root.val = successor.val
        
        # 删除后继节点
        root.right = deleteNode(root.right, successor.val)
    
    return root