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Question 1
The language [Tex]L=\{a^n b^n \mid n \geq 1\}[/Tex] is:
(GATE 2004 | MCQ | 1-mark)
regular
context-free but not regular
context-sensitive but not context-free
type-0 but not context-sensitive
Question 2
In a pushdown automaton P=(Q,Σ,Γ,δ,q0,F), a transition of the form,
👁 Imagewhere p,q∈Q, a∈σ∪{ϵ}, X,Y,∈Γ∪{ϵ}, represents
(q,Y) ∈ δ(p,a,X) Consider the following pushdown automaton over the input alphabet Σ={a,b} and stack alphabet Γ={#,A}.
👁 ImageThe number of strings of length 100 accepted by the above pushdown automaton is ___________ .
50
100
55
45
Question 3
According to the formal 7-tuple definition of a Pushdown Automaton [Tex]M=(Q,\Sigma,\Gamma,\delta,q_0,Z,F)[/Tex], the transition function $\delta$ determines the machine's next move based on exactly three input parameters. What are these three parameters?
Current state, next input symbol, and the entire stack contents
Current state, next input symbol (or ϵ), and the symbol at the top of the stack
Current state, next input symbol, and the initial stack symbol Z
Initial state, next input symbol (or ϵ), and the top of the stack
Question 4
Consider the NPDA 〈Q = {q0, q1, q2}, Σ = {0, 1}, Γ = {0, 1, ⊥}, δ, q0, ⊥, F = {q2}〉, where (as per usual convention) Q is the set of states, Σ is the input alphabet, Γ is stack alphabet, δ is the state transition function, q0 is the initial state, ⊥ is the initial stack symbol, and F is the set of accepting states, The state transition is as follows:
👁 Q60
Which one of the following sequences must follow the string 101100 so that the overall string is accepted by the automaton?
10110
10010
01010
01001
Question 5
The language {am bn Cm+n | m, n ≥ 1} is
regular
context-free but not regular
context sensitive but not context free
type-0 but not context sensitive
Question 7
Let fsa and pda be two predicates such that fsa(x) means x is a finite state automaton, and pda(y) means that y is a pushdown automaton. Let equivalent be another predicate such that equivalent (a, b) means a and b are equivalent. Which of the following first order logic statements represents the following:
Each finite state automaton has an equivalent pushdown automaton.
👁 q31
A
B
C
D
Question 8
Consider the transition diagram of a PDA given below with input alphabet ∑ = {a, b}and stack alphabet Γ = {X, Z}. Z is the initial stack symbol. Let L denote the language accepted by the PDA.
A
B
C
D
Question 9
Consider the following languages:
L1 = {anbmcn : m, n >= 1}
L2 = {anbnc2n : n >= 1}
Which one of the following is TRUE?
Both L1 and L2 are context-free.
L1 is context-free while L2 is not context-free.
L2 is context-free while L1 is not context-free.
Neither L1 nor L2 is context-free.
Question 10
For Σ = {a, b}, let us consider the regular language
L = {x ∣ x = a2 + 3k or x = b10 + 12k, k ≥ 0}
Which one of the following can be a pumping length (the constant guaranteed by the pumping lemma) for L?
3
5
9
24
There are 10 questions to complete.