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language-identification

GATE CSE & IT · Context-Free Languages · 2001-2025

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9
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Hopcroft-Ullman / Dragon Book

Automata, languages, parsing, syntax-directed translation

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2025 PYQ

Consider the following two languages over the alphabet $\{a, b, c\}$, where $m$ and $n$ are natural numbers. $$\begin{aligned} & L_1=\left\{a^m b^m c^{m+n} \mid m, n \geq 1\right\}...

mediumanswer keybasic explanation
2022 PYQ

Consider the following languages: L 1 = {a n wa n | w $$\in$$ {a, b}*} L 2 = {wxw R | w, x $$\in$$ {a, b}*, | w | , | x | > 0} Note that w R is the reversal of the string w. Which...

mediumanswer keybasic explanation
2020 PYQ

Consider the following languages. L 1 = {wxyx | w, x, y ∈ (0 + 1) + } L 2 = {xy | x, y ∈ (a + b)*, |x| = |y|, x ≠ y} Which one of the following is TRUE?

hardanswer keybasic explanation
2018 PYQ

Consider the following languages: $$\,\,\,\,\,\,\,\,{\rm I}.\,\,\,\,\,\,\,$$ $$\left\{ {{a^m}{b^n}{c^p}{d^q}} \right.|m + p = n + q,$$ where $$\left. {m,n,p,q \ge 0} \right\}$$ $$\...

mediumanswer keybasic explanation
2015 PYQ

Which of the following languages is/are regular? $${L_1}:\left\{ {wx{w^R}|w,x\, \in \left\{ {a,b} \right\}{}^ * } \right.$$ and $$\left. {\left| w \right|,\left| x \right| > 0} \ri...

mediumanswer key
2010 PYQ

Consider the languages $$$\eqalign{ & {L_1} = \left\{ {{0^i}{1^j}\,\left| {i \ne j} \right.} \right\},\,{L_2} = \left\{ {{0^i}{1^j}\,\left| {i = j} \right.} \right\}, \cr & {L_3} =...

mediumanswer key
2009 PYQ

Which one of the following languages over the alphabet $$\left\{ {0,\left. 1 \right)} \right.$$ is described by the regular expression $${\left( {0 + 1} \right)^ * }0{\left( {0 + 1...

easyanswer key
2006 PYQ

If $$s$$ is a string over $${\left( {0 + 1} \right)^ * }$$ then let $${n_0}\left( s \right)$$ denote the number of $$0'$$ s in $$s$$ and $${n_1}\left( s \right)$$ the number of $$1...

mediumanswer key
2001 PYQ

Consider the following languages: $${L_1} = \left\{ {w\,w\left| {w \in {{\left\{ {a,\,b} \right\}}^ * }} \right.} \right\}$$ $${L_2} = \left\{ {w\,{w^R}\left| {w \in {{\left\{ {a,\...

mediumanswer key