code: public Stack<MDAGNode> getTransitionPathNodes(String str)
      {
          Stack<MDAGNode> nodeStack = new Stack<MDAGNode>();
          
          MDAGNode currentNode = this;
          int numberOfChars = str.length();
          
          //Iteratively _transition through the MDAG using the chars in str,
          //putting each encountered node in nodeStack
          for(int i = 0; i < numberOfChars && currentNode != null; i++)
          {
              currentNode = currentNode.transition(str.charAt(i));
              nodeStack.add(currentNode);
          }
          /////
           
          return nodeStack;
      }
docs: 获取一个字符串路径上经过的节点<br>
  Retrieves the nodes in the _transition path starting
  from this node corresponding to a given String .
  
  @param str       a String corresponding to a _transition path starting from this node
  @return          a Stack of MDAGNodes containing the nodes in the _transition path
  denoted by {@code str}, in the order they are encountered in during transitioning