1. 主要思想
      循环前，generate root，入队；
      循环中， 队列出队并作为root，产生childs，逐个node验证是否目标,不是则push入队。

2. 代码示例
<code:C++>
class Palace;
classNode
{
   virtual bool IsTarget()const;
   virtual Node* NextChild(void*);
   virtual bool operator < (const Node& node)const;
   virtual bool operator == (const Node& node)const;
   static Palace* pPalace_;
};

Node* Node::NextChild(void* )
{
   ……
      if (HasChildNode())
         return pPalace->AddNode(ChildNode);
      else
         return 0;
}

class Palace
{
public:
   set<Node> nodes;
   queue<Node*> pNodes;
   Node* AddNode(const Node& node);
   Node* bfs_search(void* );
}

Node* Palace::bfs_search(void* )
{
    Node * pNode;
    Node* pChild = 0;
    Node root(source_state);//source_state from void*
    pNodes.push(&(*nodes.insert(root).first));
    while (pNodes.size() < MAX_NODE_COUNT)
    {
        assert(pNode = pNodes.front());
        for (each eligible arg )//arg from void*
        {
            if (pChild = pNode->NextChild(arg))
            {
                pNodes.push(pChild);
                if (pChild->IsTarget(target_state))//target_state from void*
                {
                       return pChild;
                }
            }
        }
        pNodes.pop();
    }
}
</code>