二叉树的遍历 我的

    private static void preOrder(Node root){
        if (root != null){
            //先访问根节点 打印 然后左节点 右节点
            System.out.print(root.val+"->");
            preOrder(root.left);
            preOrder(root.right);
        }
    }

    private static void iteratorPreOrder(Node root){
        Stack<Node> stack = new Stack<Node>();
        stack.push(root);
        while (!stack.empty()){
            Node cur = stack.pop();
            if (cur != null){
                System.out.print(cur.val+"->");
                stack.push(cur.right);
                stack.push(cur.left);
            }
        }
    }

    private static void inOder(Node root){
        if (root != null){
            inOder(root.left);
            System.out.print(root.val+"->");
            inOder(root.right);
        }
    }

    //left root right  加入的时候按顺序加入 root left 依次弹出 那么为cur = left  if(cur.right==null) 继续弹

    private static void iteratorInOrder(Node root){
        Stack<Node> stack = new Stack<Node>();
        Node cur = root;
        while (cur != null || !stack.empty()){
            while (cur != null){
                //把root 和 左节点 加入
                stack.push(cur);
                cur=cur.left;
            }
            cur = stack.pop();
            System.out.print(cur.val+"->");
            cur = cur.right;
        }
    }

    private static void postOrder(Node root){
        if (root != null){
            preOrder(root.left);
            preOrder(root.right);
            System.out.println(root.val);
        }
    }

    private static void iteratorPostOrder(Node root){
        LinkedList<Integer> arrayList = new LinkedList<Integer>();
        Stack<Node> stack = new Stack<Node>();
        Node p = root;
        while (p != null || !stack.empty()){
            if (p != null){
                stack.push(p);
                arrayList.addFirst(p.val);
                p = p.right;
            }else {
                Node node = stack.pop();
                p = node.left;
            }
        }
    }
}