# GATE2002-21

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We require a four state automaton to recognize the regular expression $(a\mid b)^*abb$

1. Give an NFA for this purpose
2. Give a DFA for this purpose

edited

NFA for regular expression $(a+b)^*abb$ and its equivalent DFA will be as follows: edited
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@Praveen Saini Sir What is the meaning of (a/b)* the question,is it (a+b)* what they have meant?

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yes, afai think
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praveen sir u r the best toc expert ever i seen
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state   a          b

qo     q0q1    q0

q1        ^         q2

q2       ^           q3

q3       ^           ^

q0q1     q0q1     q0q2

q0q2      q0q1     q0q3

q0q3       q0q1     q0

q3 is final state so q0q3 also final state. Total 6 states.

Where am I going wrong? Pls help @Praveen Saini

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@ , there is no need of q1, q2 and q3 check once.

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@Praveen Saini sir construct an NFA for regular expression (a+b)* abb  and then convert it into DFA, will that be okk sir ??

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Yes, this is good, but it is a time-consuming process, we can make DFA from the regular expression.
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How you will make DFA directly?
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it comes from practise

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