二分搜索树非递归(栈)实现遍历

// 二分搜索树的非递归前序遍历
    public void preOrderNR() {
        // 声明一个栈,模拟系统栈
        Stack<Node> stack = new Stack<>();
        stack.push(root);
        while (!stack.isEmpty()) {
            Node cur = stack.pop();
            System.out.println(cur.e);
            if (cur.right != null)
                stack.push(cur.right);
            if (cur.left != null)
                stack.push(cur.left);
        }
    }