Let the regular expression $R = ((a^*\cup \emptyset \cup \varepsilon^*)^*b)^*$ above $\Sigma = \{a,b,c,d\}$. What is the minimal number of states for a DFA accepting this regex?
- $1$
- $2$
- $4$
- $5$ or more
So for my understanding, this regex is equivalent to $(a^*b)^*$. I was able to build the following DFA, nevertheless, I know the answer is $2$. How is it possible?