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GATE CSE & IT · Context-Free Languages · 1992-2026

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Hopcroft-Ullman / Dragon Book

Automata, languages, parsing, syntax-directed translation

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2026 PYQ

Let $\Sigma=\{a, b, c, d\}$ and let $L=\left\{a^i b^j c^k d^l \mid i, j, k, l \geq 0\right\}$. Which of the following constraints ensure(s) that the language $L$ is context-free?

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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\}...

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2019 PYQ

Which one of the following languages over $\Sigma=\{a, b\}$ is NOT context-free?

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2015 PYQ

Which of the following languages are context-free? $$$\eqalign{ & {L_1} = \left\{ {{a^m}{b^n}{a^n}{b^m}|m,n \ge 1} \right\} \cr & {L_2} = \left\{ {{a^m}{b^n}{a^m}{b^n}|m,n \ge 1} \...

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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} =...

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2009 PYQ

Which one of the following is FALSE?

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2002 PYQ

The language accepted by a pushdown Automation in which the stack is limited to $$10$$ items is best described as

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1999 PYQ

Let $${L_D}$$ be the set of all languages accepted by a $$PDA$$ by final state and $${L_E}$$ the set of all languages accepted by empty stack. Which of the following is true?

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1998 PYQ

Regarding the power of recognition of languages, which of the following statement is false?

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1992 PYQ

In which of the cases stated below is the following statement true? “For every non-deterministic machine $${M_1}$$ there exists an equivalent deterministic machine $${M_2}$$ recogn...

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