Convert regular expression to DFA How do you construct a DFA from a  language that has a + sign? e.g. $L = \{(a+b)\}*$
In this case + stands for the OR-operation. So the automaton is indifferent using an $a$ transition or a $b$ transition.

It's sufficient to construct an automaton with one state which is initial and final state and having one transition labeled with a, b.