code: protected Node<V> cleanNodePath(int number,int layout,Node<V> currentNode)
  	{
  		if(layout<0)
  		{//超出范围
  			return null;
  		}
  		layout--;
  		int p=getMaskValue(number,layout);
  		Node<V>[] sub=currentNode.getSub();
  		Node<V> node=sub[p];
  		if(node==null)
  		{//不可达
  			return null;
  		}
  		if(layout==0)
  		{//到达终点
  			sub[p]=null;
  			return node;
  		}
  		Node<V> next=cleanNodePath(number, layout,node);
  		return next;
  	}
docs: 清理路径
  @param number
  @param layout
  @param currentNode
  @return