gistfile1.erl

-module(t).
-compile(export_all).

merge([], NewTree)->
    NewTree;

merge([{Node, Ch}|Tail], NewTree) ->
   case lists:member(Node, NewTree) of
       true -> merge(Tail, NewTree);
       false -> merge(Tail, [{Node, Ch}|NewTree])
   end.
   

add_to_tree_iter(Tree, _, [], NewTree) ->
    merge(Tree, NewTree);

add_to_tree_iter(Tree, Parent, [Child| Childs], NewTree) ->
    case proplists:get_value(Parent, Tree) of
        undefined -> add_to_tree_iter(Tree, Child, Childs, [{Parent, [Child]}|NewTree]);
        HChilds when is_list(HChilds) -> 
               NChilds = case lists:member(Child, HChilds) of
                             false -> [Child|HChilds];
                             true -> HChilds
                         end,
               add_to_tree_iter(Tree, Child, Childs, [{Parent, NChilds}|NewTree])
    end.

add_to_tree(Tree, [From| Childs]) ->
    add_to_tree_iter(Tree, From, Childs, []).