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Read the following and answer the questions that follow.

A machine is represented by states Q, input alphabet Σ, transition function δ. Initial state q0 and final state F. The machine accepts all the strings over Σ = {a, b}, which start and ended with any combination of all alphabet and abb works /lies as substring in all the strings to be accepted.

For the above mentioned passage which of the following is correct?

This question was previously asked in
UGC NET 2024 Management Question Paper (02-Sep-2024) (Shift 2)
The correct answer is
Four-state chain automaton with loops on a, b at start and accepting states

The passage describes the language of all strings over {a, b} in which abb occurs somewhere, with any string of a's and b's allowed before and after it: \((a+b)^{*}abb(a+b)^{*}\). A nondeterministic automaton for it guesses where abb starts, reads abb, and then stays accepting whatever follows.

Step 1 — Freedom before the pattern requires a self-loop on a, b at the start state 1.

Step 2 — The pattern itself is the chain 1 –a→ 2 –b→ 3 –b→ 4.

Step 3 — Freedom after the pattern requires a self-loop on a, b at the accepting state 4.

Only the drawing with self-loops on a, b at both state 1 and accepting state 4 has all three parts.

The drawing with a loop only at state 1 accepts strings that end with abb, so a string such as abba is wrongly rejected. The drawing with a loop only at state 4 accepts strings that begin with abb, so babb is wrongly rejected. The drawing whose start state 1 is itself accepting with a loop on a, b accepts every string, including the empty string and bbb, which do not contain abb.

The automaton 1 –a→ 2 –b→ 3 –b→ 4 with self-loops on a, b at both state 1 and accepting state 4 option is correct.

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Similar Questions

  1. There are exactly __________ different finite automata with three states x, y and z over the alphabet {a, b} where x is always the start state.

  2. The transition function for the language \(L = \{w \mid n_{a}(w)\) and \(n_{b}(w)\) are both odd\(\}\) is given by :

    \(\delta(q_{0}, a) = q_{1}\) ; \(\delta(q_{0}, b) = q_{2}\)

    \(\delta(q_{1}, a) = q_{0}\) ; \(\delta(q_{1}, b) = q_{3}\)

    \(\delta(q_{2}, a) = q_{3}\) ; \(\delta(q_{2}, b) = q_{0}\)

    \(\delta(q_{3}, a) = q_{2}\) ; \(\delta(q_{3}, b) = q_{1}\)

    The initial and final states of the automata are :

  3. Minimal deterministic finite automaton for the language \(L = \{0^{n} \mid n \geq 0, n \neq 4\}\) will have :

  4. For the above specified passage, which of the following is DFA for the language represented/accepeted by machine?

  5. Which of the following represented the minimum state DFA for the above specified passage?

  6. Which of the following languages can be recognized by neither Non-Deterministic Finite Automata (NFA) nor Deterministic Finite Automata (DFA) ?

    (A) L1 = {w ∈ {0, 1}* | the length of w is even}

    (B) L2 = {w ∈ {0, 1}* | the length of w is odd}

    (C) L3 = {w ∈ {0, 1}* | all 0′s come before all 1′s in w}

    (D) L4 = {w ∈ {0, 1}* | w contains an equal number of 0′s and 1′s}

    (E) L5 = {w ∈ {0, 1}* | all 1′s come before all 0′s in w}

    Choose the correct answer from the options given below :

  7. Which of the following Finite Automata, recognizes the language L={a,b}* ?

    A. M=({q0}, {a,b}, δ, q0, {q0}) where, δ is

    ab
    q0{q0}{q0}

    B. M=({q0,q1}, {a,b}, δ, q0, {q0,q1}) where, δ is

    ab
    q0{q0,q1}{q0,q1}
    q1{q1}{q1}

    C. M=({q0,q1}, {a,b}, δ, q0, {q0,q1}) where, δ is

    ab
    q0{q0,q1}{q0}
    q1-{q1}

    D. M=({q0,q1,q2 }, {a,b}, δ, q0, {q0}) where, δ is

    ab
    q0{q0}{q0}
    q1{q2}-
    q2{q0}{q2}
  8. What is the minimum and maximum number of initial, dead, unreachable and final states in a valid ‘n’ state finite automaton, where the language accepted is not ‘φ’?

  9. Let L be the language generated by regular expression 0*10* and accepted by the deterministic finite automata M, whose transition table is given below (start state a; final states c, d and e).

    State01
    abc
    bad
    cef
    def
    eef
    fff

    Consider the relation RM defined by M. As all states are reachable from the start state, RM has _____ equivalence classes.


Important Questions from Finite Automata

  1. Consider the DFA given below

    Which of the regular expressions given below represents the above DFA ?

  2. Let $M$ be a nondeterministic finite automaton (NFA) with 6 states over a finite alphabet.
    Which of the following options CANNOT be the number of states in the minimal deterministic finite automaton (DFA) that is equivalent to $M$ ?
  3. Consider the following deterministic finite automaton (DFA) defined over the alphabet, Σ = {𝑎, 𝑏}. Identify which of the following language(s) is/are accepted by the given DFA.

  4. Consider a finite state machine (FSM) with one input 𝑋 and one output 𝑓, represented by the given state transition table. The minimum number of states required to realize this FSM is ________. (Answer in integer)

    Present stateNext stateOutput f
    X = 0X = 1X = 0X = 1
    AFB00
    BDC00
    CFE00
    DGA10
    EDC00
    FFB11
    GH001
    HGA10
  5. Consider the following DFA that generates set of strings over $\Sigma=\{a, b, c\}$

    Now identify that which of the followings is the best description of the language for the above DFA

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