PDA (pushdown automaton)
- 2. Our Topic PDA (pushdown automaton)
- 3. GROUP MEMBER NAME S.ID Zaheer Raihan Shah Alam Shagor 011151053 011151052
- 4. Pushdown Automaton (PDA) A Pushdown Automaton is a nondeterministic finite state automaton (NFA) that permits ε-transitions and a stack.
- 5. Pushdown Automaton -- PDA Input String Stack States
- 7. The States q1 q2 a, b c Input symbol Pop symbol Push symbol
- 8. q1 q2 a, b c a b top input stack a Replace e h $ e h $ c
- 9. q1 q2 a, c a a Push b e h $ e h $ b c top input stack
- 10. q1 q2 a, b a a Pop b e h $ e h $ top input stack
- 11. q1 q2 a, a a No Change b e h $ e h $ btop input stack
- 12. Non-Determinism q1 q2a, b c q3 a, b c q1 q2 , b c transition These are allowed transitions in a Non-deterministic PDA (NPDA)
- 13. NPDA: Non-Deterministic PDA Example: , a, a b, a q0 q1 q2 q3 b, a , $ $
- 14. a, a b, a 0q q1 q2 q3 Execution Example: Input a a a b b b current state b, a Time 0 , , $ $ Stack $
- 15. a, a b, a q0 q1 q2 q3 Input a a a b b b b, a Time 1 , , $ $ Stack $
- 16. a, a b, a q0 q1 q2 q3 Input Stack a a a b b b $ a b, a Time 2 , , $ $
- 17. a, a b, a q0 q1 q2 q3 Input Stack a a a b b b $ a a b, a Time 3 , , $ $
- 18. a, a b, a q0 q1 q2 q3 Input Stack a a a b b b $ a a a b, a Time 4 , , $ $
- 19. a, a b, a q0 q1 q2 q3 Input a a a b b b Stack $ a a a b, a Time 5 , , $ $
- 20. a, a b, a q0 q1 q2 q3 Input a a a b b b $ a Stack b, a Time 6 , , $ $ a
- 21. a, a b, a q0 q1 q2 q3 Input a a a b b b $ Stack b, a Time 7 , , $ $ a
- 22. a, a b, a q0 q1 q2 q3 Input a a a b b b b, a Time 8 accept , , $ $ $ Stack
- 23. A string is accepted if there is a computation such that: • All the input is consumed • The last state is a final state At the end of the computation, we do not care about the stack contents The Language of PDA
- 25. THE END