链式二叉树的后序创建、递归后序遍历、非递归堆栈后序遍历、后序销毁
Post-order creation of chained binary trees, recursive post-order traversal, non-recursive stack post-order traversal, post-order destruction
Post-order creation of chained binary trees, recursive post-order traversal, non-recursive stack post-order traversal, post-order destruction