学步园

void PreorderThreading (Tree * const ptree) ;<br /> static void Preorder_Threading (Tree * const ptree, Node * * const previous) ;<br /> void PreorderThreadedTraversal (const Tree tree, void (* pfun) (const Item item)) ;</p> <p>void PreorderThreading (Tree * const ptree)<br /> {<br /> Node * previous = NULL ;</p> <p> Preorder_Threading (ptree, &previous) ;<br /> }</p> <p>static void Preorder_Threading (Tree * const ptree, Node * * const previous)<br /> {<br /> if (*ptree != NULL)<br /> {<br /> if (NULL == (*ptree) -> left)<br /> {<br /> (*ptree) -> left_tag = THREAD ;<br /> (*ptree) -> left = *previous ;<br /> }<br /> if (*previous != NULL)<br /> {<br /> if (NULL == (*previous) -> right)<br /> {<br /> (*previous) -> right_tag = THREAD ;<br /> (*previous) -> right = *ptree ;<br /> }<br /> }<br /> *previous = *ptree ;<br /> if (NULL == (*previous) -> right && LINK == (*previous) -> right_tag)<br /> (*previous) -> right_tag = THREAD ;<br /> if (LINK == (*ptree) -> left_tag)<br /> Preorder_Threading (&(*ptree) -> left, previous) ;<br /> if (LINK == (*ptree) -> right_tag)<br /> Preorder_Threading (&(*ptree) -> right, previous) ;<br /> }<br /> }</p> <p>void PreorderThreadedTraversal (const Tree tree, void (* pfun) (const Item item))<br /> {<br /> Node * scan = tree ;</p> <p> while (scan != NULL)<br /> {<br /> while (LINK == scan -> left_tag)<br /> {<br /> (* pfun) (scan -> item) ;<br /> scan = scan -> left ;<br /> }<br /> while (scan != NULL && THREAD == scan -> right_tag)<br /> {<br /> (* pfun) (scan -> item) ;<br /> scan = scan -> right ;<br /> }<br /> }<br /> }