Construct a PDA that matches all strings in the language over {a,b,c,d} such that each occurrence of the substring ab is eventually followed by a distinct occurrence of a substring cd (e.g.,abcdabcd and abababadcacdcdcdcd are acceptable, but cdab and ababdddcd are not).
Give a short description of the set of strings associated with each state of your PDA.


Construct a PDA that matches all strings in the language over {a,b,c,d} such that each occurrence...
Construct a PDA that matches all strings in the language over {x,y} such that each string begins and ends with the same symbol. Submit Below, give a short description of the set of strings associated with each state of your PDA ?
Give a regular expression for the language of strings over {a,b} in which each substring of length 2 contains two distinct characters
Theory of Computation - Push Down Automata (PDA) and Context
Free Grammars (CFG)
Problem 1. From a language description to a PDA Show state diagrams of PDAs for the following languages: a. The set of strings over the alphabet fa, b) with twice as many a's as b's. Hint: in class, we showed a PDA when the number of as is the same as the number of bs, based on the idea of a counter. + Can we use a...
3) Construct a regular expression defining each of the following languages over the alphabet {a, b}. (a) L = {aab, ba, bb, baab}; (b) The language of all strings containing exactly two b's. (c) The language of all strings containing at least one a and at least one b. (d) The language of all strings that do not end with ba. (e) The language of all strings that do not containing the substring bb. (f) The language of all strings...
Give regular expressions for the following languages: (a) The language of all strings over {a,b} except the empty string. (b) The language of all strings over {a,b} that contain both bab and bba as substrings. (c)L k = {w ∈ {a,b} * | w contains a substring having 3 more b’s than a’s}. (d) The language of all strings over {a,b} that have a b in every odd position (first symbol is considered position 1; empty string should be accepted)...
Construct an DFA automaton that recognizes the following language of strings over the alphabet {a,b}: the set of all strings over alphabet {a,b} that contain aa, but do not contain aba.
Give a DFA over {a,b} that accepts all strings containing a total of exactly 4 'a's (and any number of 'b's). For each state in your automaton, give a brief description of the strings associated with that state.
(20) Let L be the language over {a,b,c} accepting all strings so that: 1. No b's occur before the first c. 2. No a's occur after the first c. 3. The last symbol of the string is b. 4. Each b that is not the last symbol is immediately followed by at least two c's. 5. There are exactly as many a's as b's. Construct a context-free grammar generating L. You do not need an inductive proof, but you should...
1. Let L be the language over {a, b, c} accepting all strings so that: 1. No b's occur before the first c. 2. No a's occur after the first c. 3. The last symbol of the string is b. 4. Each b that is not the last symbol is immediately followed by at least two d's. Choose any constructive method you wish, and demonstrate that L is regular. You do not need an inductive proof, but you should explain how your construction accounts for...
1. (15) Let L be the language over {a,b,c} accepting all strings so that: 1. No b's occur before the first c. 2. No a's occur after the first c. 3. The last symbol of the string is b. 4. Each b that is not the last symbol is immediately followed by at least two c's. Choose any constructive method you wish, and demonstrate that is regular. You do not need an inductive proof, but you should explain how your...