0 votes 0 votes Let $A = \{ \langle R \rangle \mid \text{R is a regular expression describing a language containing at least one string w that has 111 as a substring} \text{(i.e., w = x111y for some x and y)\}}$. Show that $A$ is decidable. Theory of Computation michael-sipser theory-of-computation decidability proof + – admin asked Oct 17, 2019 edited Oct 17, 2019 by Lakshman Bhaiya admin 180 views answer comment Share Follow See all 0 reply Please log in or register to add a comment.