Consider a Deterministic Finite Automaton (DFA) defined as follows:
- States $(Q):\left\{q_0, q_1, q_2, q_3, q_4\right\}$
- Alphabet ( $\Sigma$ ): $\{a, b\}$
- Start State: $q_0$
- Final States $(F):\left\{q_1, q_2\right\}$
- Transition Function ( $\delta$ ):
| Current State | Input 'a' | Input 'b' |
$$
\begin{aligned}
& |:--|:--|:---| \\
& \left|\rightarrow q_0\right| q_1\left|q_2\right| \\
& \left|* q_1\right| q_1\left|q_3\right| \\
& \left|* q_2\right| q_4\left|q_2\right| \\
& \left|q_3\right| q_1\left|q_3\right| \\
& \left|q_4\right| q_4\left|q_2\right|
\end{aligned}
$$
(The arrow $\rightarrow$ indicates the start state, and the asterisk indicates a final state.)
The language recognized by this machine is:
- The set of all non-empty strings that start and end with the same symbol.
- The set of all non-empty strings that start and end with different symbols.
- The set of all strings that contain the substring aa or bb .
- The set of all strings where the total number of symbols is odd.