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void pairoff(StringTree * t1, StringTree * t2)
{ Enumeration lister1(t1), lister2(t2);
  while (lister1.hasmore() || lister2.hasmore())
  { string s1 = "", s2 = "";
    if (lister1.hasmore())
      s1=lister1.getnext();
    if (lister2.hasmore())
      s2=lister2.getnext();
    spaces(20-s1.length());
    cout << s1 << " - " << s2 << "\n"; } }

void main(void)
{ cout << "enter:\n";
  cout << "  1 word   to insert word in tree one\n";
  cout << "  2 word   to insert word in tree two\n";
  cout << "  p        to pair off trees\n";
  cout << "  x        to exit\n";
  StringTree * tree1 = NULL, * tree2 = NULL;
  while (1)
  { cout << "> ";
    string command;
    cin >> command;
    if (command=="1")
    { string operand;
      cin >> operand;
      insert(tree1, operand);
      cout << operand << " inserted into tree 1\n"; }
    else if (command=="2")
    { string operand;
      cin >> operand;
      insert(tree2, operand);
      cout << operand << " inserted into tree 2\n"; }
    else if (command=="p")
    { pairoff(tree1, tree2); }
    else if (command=="x")
    { break; }
    else
    { cout << "Get it right.\n"; } } }
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