The document discusses deterministic pushdown automata (DPDA) and provides examples of DPDAs that accept specific languages. It begins by defining DPDA as a PDA that has at most one choice of move in any state, as opposed to a non-deterministic PDA. It then gives an example of a DPDA that accepts the language L={anbn|n>1} and explains its transition function. Finally, it lists several other language recognition problems and invites the reader to design DPDAs to solve them.

1. Deterministic
Pushdown
Automata
(DPDA)
-Sampath Kumar S,
AP/CSE, SECE

2. Types of PDA
The PDA can be classified into:
1. Deterministic PDA – PDA that has at most one
choice of move in any state.
2. Non-deterministic PDA - PDA that has more than
one choice of move in any state.
21 November 2017
Sampath Kumar S, AP/CSE, SECE
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3. Problems to discuss:
111. Design a PDA which accepts L={anbn|n>1}
Solution:
 Let q0 be the initial stat, q3 be the final state and z0
be bottom of the stack.
 Read each ‘a’ and push into stack.
 Then read each ‘b’ and pop out the stack for
matching a’s.
 Where all b’s are read if the stack is empty then it is
successful
 If any a’s are left over on the stack or b’s on input
tape, it is rejected.
21 November 2017
Sampath Kumar S, AP/CSE, SECE
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4. Solution for sum 111:
The PDA moves are as follows:
δ(q0, a, z0) = (q1, az0) ….. (PUSH a)
δ(q1, a, a) = (q1, aa) ….. (PUSH a)
δ(q1, b, a) = (q2, ε) ….. (POP a)
δ(q2, b, a) = (q2, ε) ….. (POP a)
δ(q2, ε, z0) = (q3, z0) ….. (Accept and HALT)
21 November 2017
Sampath Kumar S, AP/CSE, SECE
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5. Problems to discuss:
112. Design a PDA which accept the language
containing equal number of a’s and b’s over Σ={a,
b}.
113. Design a PDA which accepts L={anb2n|n>1}
114. Design a PDA which accepts L={a3bncn|n>0}
115. Design a PDA which accepts L={wcwr|w
(a+b)*}
116. Design a PDA which accepts the set of
balanced parenthesis. ([{()}])
21 November 2017
Sampath Kumar S, AP/CSE, SECE
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6. Problems to discuss:
117. Design a PDA which accepts
L={apbncm|p+m=n}.
118. Design a PDA which accepts
L={0m1n0m|m,n>1}.
119. Design a PDA which accepts L={aibjck|i+j=k; i, j
>1}.
21 November 2017
Sampath Kumar S, AP/CSE, SECE
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7. Problems to discuss:
120. Design a PDA which accepts
L={anbmcndm|n,m>1}.
121. Design a PDA which accepts L={anb2n+1|n>1}
21 November 2017
Sampath Kumar S, AP/CSE, SECE
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8. 21 November 2017
Sampath Kumar S, AP/CSE, SECE
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9. நன்றி
21 November 2017
Sampath Kumar S, AP/CSE, SECE
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