public boolean isSymmetric(TreeNode root) {
    	boolean res = false;
    	L= new ArrayList();
    	R= new ArrayList();
    	if( root.left==null && root.right==null){
    		res = true;
    	}else if( root.left == null || root.right == null){
    		res = false;
    	}else{
    		this.inorder(root.left);
    		this.inorderR(root.right);
    		if(R.size()!=L.size()){
    			res = false;
    		}else{
    			res = true;
//CollectionTool.printList(L);
//CollectionTool.printList(R);
    			for(int i=0;i<L.size();i++){
        			if(R.get(i)!=L.get(i)){
        				res = false;
        			}
        		}
    		}
    	}
    	return res;
    }