Problem:

Write a Python $($or C$)$ function that recognizes the presence or absence of a substring of the

form $a[a-z]b[a-z]a$ in a string. The expression $[$a$-$z$]$ refers to any lower case ASCII letter

between a and z$,$ i$.$e$.$ all lower case ASCII letters.

To solve this problem, you have to find an NFA that recognizes the regular expression. You can

then either implement the NFA directly or by using an equivalent DFA. The function should

return the index of the last letter of the first occurrence of the expression. It does not need to

recognize more than one occurrence of the substring.

For example, given "aaaabaaabaa" a correct answer would be $7.$ "aabacbaa" would also yield