Grep and JavaScript RegExp convert regex string patterns into NFAs using Thompson's Construction, then convert NFA to DFA for O(N) fast text pattern matching.
Visual representation of control loops, memory layout, and execution flow for Finite Automata, Regular Languages & Chomsky Hierarchy.
Define Q (states), Σ (alphabet), δ (transition function), q0 (start state), F (final states).
Machine reads input symbol by symbol moving along matching transition arcs.
If machine ends in an accepting state (F) after full string input, string is ACCEPTED.
| Feature / Dimension | Deterministic Finite Automaton (DFA) | Nondeterministic Finite Automaton (NFA) |
|---|---|---|
| Next State Transition | Exactly ONE next state for each (State, Symbol) pair | Can transition to ZERO, ONE, or MULTIPLE next states |
| Epsilon (ε) Moves | Does NOT allow ε-transitions (spontaneous state moves without reading input) | Allows ε-transitions |
| Expressive Power | Identical language power to NFA (every NFA can be converted to equivalent DFA) | Identical language power to DFA |
Detailed answers, interviewer pro tips, key takeaway summaries, and code examples formulated for technical rounds.
✅ Correction: NFA and DFA recognize the exact same set of Regular Languages. Subset Construction algorithm converts any NFA to an equivalent DFA.
Classification of formal grammars and recognizing machines.