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Regular expressions and finite automata, Context-free grammars and push-down automata, Regular and context-free languages, Pumping lemma, Turing machines and undecidability.

$$\scriptsize{\overset{{\large{\textbf{Mark Distribution in Previous GATE}}}}{\begin{array}{|c|c|c|c|c|c|c|c|}\hline
\textbf{Year}& \textbf{2022} & \textbf{2021-1}&\textbf{2021-2}&\textbf{2020}&\textbf{2019}&\textbf{2018}&\textbf{2017-1}&\textbf{2017-2}&\textbf{2016-1}&\textbf{2016-2}&\textbf{Minimum}&\textbf{Average}&\textbf{Maximum}
\\\hline\textbf{1 Mark Count} & 2 &2&3&3&2&2&2&3&3&3&2&2.5&3
\\\hline\textbf{2 Marks Count} & 3 &3&4&3&3&3&5&3&3&3&3&3.3&5
\\\hline\textbf{Total Marks} & 8 &8&11&9&8&8&12&9&9&9&\bf{8}&\bf{9.1}&\bf{12}\\\hline
\end{array}}}$$

Previous GATE Questions in Theory of Computation

54 votes
4 answers
151
29 votes
5 answers
153
Consider the finite automaton in the following figure: What is the set of reachable states for the input string $0011$?$\{q_0,q_1,q_2\}$$\{q_0,q_1\}$$\{q_0,q_1,q_2,q_3\}$...
23 votes
3 answers
157
39 votes
4 answers
158
Let $L$ be the set of all binary strings whose last two symbols are the same. The number of states in the minimal state deterministic finite state automaton accepting $L$...
41 votes
7 answers
159
37 votes
4 answers
162
24 votes
4 answers
163
34 votes
2 answers
169
Show that the language $$L = \left\{ xcx \mid x \in \left\{0,1\right\}^* \text{ and }c\text{ is a terminal symbol}\right\}$$ is not context free. $c$ is not $0$ or $1$.