7 votes 7 votes Find regular expressions for: All binary strings with exactly two $1’s$ The set $\{a^nb^m :n\geq3, m$ is even$\}$ All binary strings with a double symbol (contains $00$ or $11$) somewhere. The language on $\Sigma=\{a,b\}, L=\{w:n_a(w) \mod 3=0\}$ Theory of Computation theory-of-computation regular-language finite-automata + – Garrett McClure asked Sep 22, 2017 • edited Aug 8, 2021 by soujanyareddy13 Garrett McClure 1.3k views answer comment Share Follow See all 0 reply Please log in or register to add a comment.
Best answer 8 votes 8 votes $1.L_{1}=0^{*}10^{*}10^{*}$ $2.L_{2}=aaaa^{*}\left ( bb \right )^{*}$ $3.L_{3}=\left ( 0+1 \right )^{*}00\left ( 0+1 \right )^{*}+\left ( 0+1 \right )^{*}11\left ( 0+1 \right )^{*}$ $4.L_{4}=b^{*}(ab^{*}ab^{*}ab^{*})^{*}$ sourav. answered Sep 22, 2017 • edited Sep 25, 2017 by sourav. sourav. comment Share Follow See all 11 Comments See all 11 11 Comments reply Arjun commented Sep 23, 2017 reply Follow Share For $L_4$, b is not accepted. 1 votes 1 votes sourav. commented Sep 23, 2017 reply Follow Share sir $L_{4}=(b^{*}ab^{*}ab^{*}ab^{*})^{+}?$ 0 votes 0 votes Pawan Kumar 2 commented Sep 23, 2017 reply Follow Share can we write L1 as (110* + 0*110*+ 0*10*1+10*10*) ? I know L1=0*10*10* covers it , but still is above is also correct? 0 votes 0 votes Arjun commented Sep 23, 2017 reply Follow Share No, that also won't accept b rt? We should allow no a's because 0 is divisible by 3. 0 votes 0 votes sourav. commented Sep 23, 2017 reply Follow Share Sir , i am not getting you . If you are saying that my $L_{4}$ should accept $b$,then my $L_{4}$ is actually accepting $b$ $L_{4}=b^{1}(b^{*}ab^{*}ab^{*}ab^{*})^{0}b^{0}$ Actually i too though that $n(a)=0$ should be accpeted as 0 is divisible by 3 0 votes 0 votes Arjun commented Sep 23, 2017 reply Follow Share yes, sorry I missed that. But you can avoid b* at end. 0 votes 0 votes sourav. commented Sep 23, 2017 reply Follow Share okk sir , thank you :) 0 votes 0 votes OO7 commented Sep 24, 2017 reply Follow Share thank you Sir 0 votes 0 votes Diksha Aswal commented Sep 25, 2017 reply Follow Share for L4 why not b*(ab*ab*ab*)* ? 0 votes 0 votes sourav. commented Sep 25, 2017 reply Follow Share @diksha , yes you are correct.Thanks 0 votes 0 votes akash.dinkar12 commented Sep 29, 2017 reply Follow Share L4 can also be expressed as (b + ab*ab*a)* 0 votes 0 votes Please log in or register to add a comment.
1 votes 1 votes solution Ans1. 0*10*10* stdntlfe answered Sep 23, 2017 stdntlfe comment Share Follow See all 0 reply Please log in or register to add a comment.
0 votes 0 votes ......... abhishekmehta4u answered Mar 30, 2019 • edited Mar 30, 2019 by abhishekmehta4u abhishekmehta4u comment Share Follow See all 0 reply Please log in or register to add a comment.