广度优先遍历

	public List<TreeNode> breadFirst(){
		Queue<TreeNode> queue=new ArrayDeque<TreeNode>();
		List<TreeNode> list=new ArrayList<ThreeLinkBinTree.TreeNode>();
		if(root!=null){
			queue.offer(root);
		}
		while(!queue.isEmpty()){
			list.add(queue.peek());
			TreeNode p=queue.poll();
			if(p.left!=null){
				queue.offer(p.left);
			}
			if(p.right!=null){
				queue.offer(p.right);
			}
		}
		return list;
	}