【JAVA】二叉树的非递归中序遍历

    public List inorderTraversal(TreeNode root) {
    	System.out.println("中序遍历");
        List list = new ArrayList();
        if(root!=null){
        	
            Stack stack = new Stack();
            while(!stack.isEmpty() || root!=null){
                if(root!=null){
                    stack.push(root);
                    root = root.left;
                } else{
                    root = stack.pop();
                    list.add(root.val);
                    root = root.right;
                }
            }
        }
        return list;
    }