let creer x = (
    let tree = vide() in
    let currentTree = tree in
        List.iter(fun item ->
            for i = 0 to (String.length item) - 1 do
                let letter =  (String.get item i) in
                let Noeud(_, childs) = currentTree in
                let letterFoundInChilds = false in
                let rec check_if_letter_exists c = match c with
                | [] -> ()
                | current::next -> (
                    let (childLetter, childTree) = current in
                    if childLetter = letter then (
                        letterFoundInChilds = true;
                        currentTree = childTree;
                        ();
                    ) else check_if_letter_exists next;
                ) in check_if_letter_exists !childs;
                if letterFoundInChilds = false then (
                    let isLastLetter = (i = (String.length item) - 1);
                    let newTree = (letter, Noeud(ref isLastLetter, ref []));
                    !childs @ [newTree];
                ) in
                print_endline (String.make 1 letter);
            done
        ) listeMots
)