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struct LittleNote
{ StringTree * tree;
  int position;
  LittleNote(void) { }
  LittleNote(StringTree * t, int pos): tree(t), position(pos) { } };

struct Enumeration
{ LittleNote stack[100];
  int numinstack;
  bool nextisknown;
  string next;

  Enumeration(StringTree * t) { stack[0]=LittleNote(t,1); numinstack=1;
                                nextisknown=false; next=""; }

  void push(LittleNote n)
  { stack[numinstack] = n;
    numinstack += 1; }

  LittleNote pop(void)
  { numinstack -= 1;
    return stack[numinstack]; }

  void preparenext(void)
  { while (numinstack>0)
    { LittleNote note = pop();
      StringTree * t = note.tree;
      switch (note.position)
      {
        case 1: { if (t!=NULL)
                  { push(LittleNote(t, 2));
                    push(LittleNote(t->left, 1)); }
                  break; }

        case 2: { push(LittleNote(t->right, 1));
                  next = t->data;
                  nextisknown = true;
                  return; } } }
    nextisknown = false; }

  bool hasmore(void)
  { if (nextisknown)
      return true;
    preparenext();
    return nextisknown; }

  string getnext(void)
  { if (!nextisknown)
      preparenext();
    nextisknown = false;
    return next; } };

void print(StringTree * t)
{ Enumeration lister(t);
  while (lister.hasmore())
    cout << lister.getnext() << "\n"; }
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