// function List ----------------------------------
void List(PNODE tree,char* s,int& sp)
{
  NODE n;
  PNODE p;
 
  n.value = Next(s,sp);
  n.lch = n.rch = NULL;
  if (tree == NULL) 
    tree = &n;
  else{
    p = tree;
    while(1) {
      if (n.value < p->value) {
        if (p->lch == NULL) {
          p->lch = &n;
          break;
        }else
          p = p->lch;
      }else{
        if (p->rch == NULL) {
          p->rch = &n;
          break;
        }else
          p = p->rch;
      }
    }//endwhile
  }

  if (Next(s,sp) == -1) {  // we parsed the whole string
    Show(tree);            // display the characters
    putchar('\n');
  }else
    List(tree,s,sp);
}//end List