1
GATE CSE 2020
MCQ (Single Correct Answer)
+2
-0.67

Consider the following languages.

L1 = {wxyx | w, x, y ∈ (0 + 1)+}

L2 = {xy | x, y ∈ (a + b)*, |x| = |y|, x ≠ y}

Which one of the following is TRUE?

A
L1 is regular and L2 is context-free.
B
L1 is context-free but not regular and L2 is context-free.
C
Neither L1 nor L2 is context-free.
D
L1 is context-free but L2 is not context-free.
2
GATE CSE 2019
MCQ (Single Correct Answer)
+2
-0.67

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

A
$\left\{w w^R \mid w \in\{a, b\}^*\right\}$
B
$\left\{w a^n b^n w^R \mid w \in\{a, b\}^*, n \geq 0\right\}$
C
$\left\{w a^n w^R b^n \mid w \in\{a, b\}^*, n \geq 0\right\}$
D
$\left\{a^n b^i \mid i \in\{n, 3 n, 5 n\}, n \geq 0\right\}$
3
GATE CSE 2018
MCQ (Single Correct Answer)
+2
-0.6
Consider the following languages:

$$\,\,\,\,\,\,\,\,{\rm I}.\,\,\,\,\,\,\,$$ $$\left\{ {{a^m}{b^n}{c^p}{d^q}} \right.|m + p = n + q,$$ where $$\left. {m,n,p,q \ge 0} \right\}$$
$$\,\,\,\,\,\,{\rm II}.\,\,\,\,\,\,\,$$ $$\left\{ {{a^m}{b^n}{c^p}{d^q}} \right.|m = n$$ and $$p=q,$$ where $$\left. {m,n,p,q \ge 0} \right\}$$
$$\,\,\,\,{\rm III}.\,\,\,\,\,\,\,$$ $$\left\{ {{a^m}{b^n}{c^p}{d^q}} \right.|m = n = p$$ and $$p \ne q,$$ where $$\left. {m,n,p,q \ge 0} \right\}$$
$$\,\,\,\,{\rm IV}.\,\,\,\,\,\,\,$$ $$\left\{ {{a^m}{b^n}{c^p}{d^q}} \right.|mn = p + q,$$ where $$\left. {m,n,p,q \ge 0} \right\}$$

Which of the languages above are context-free?

A
$${\rm I}$$ and $${\rm IV}$$ only
B
$${\rm I}$$ and $${\rm II}$$ only
C
$${\rm II}$$ and $${\rm III}$$ only
D
$${\rm II}$$ and $${\rm IV}$$ only
4
GATE CSE 2016 Set 1
MCQ (Single Correct Answer)
+2
-0.6
Consider the following context-free grammars:
$$\eqalign{ & {G_1}:\,\,\,\,\,S \to aS|B,\,\,B \to b|bB \cr & {G_2}:\,\,\,\,\,S \to aA|bB,\,\,A \to aA|B|\varepsilon ,\,\,B \to bB|\varepsilon \cr} $$

Which one of the following pairs of languages is generated by $${G_1}$$ and $${G_2}$$, respectively?

A
$$\left\{ {{a^m}{b^n}|m > 0\,\,\,\,} \right.$$ or $$\,\,\,\,$$$$n > \left. 0 \right\}$$ and $$\left\{ {{a^m}{b^n}|m > 0\,\,\,\,} \right.$$ and $$\,\,\,\,n > \left. 0 \right\}\,\,\,\,$$
B
$$\left\{ {{a^m}{b^n}|m > 0\,\,\,\,} \right.$$ and $$\,\,\,n > \left. 0 \right\}\,\,\,\,$$ and $$\left\{ {{a^m}{b^n}|m > 0\,\,\,\,} \right.$$ or $$\,\,\,\,n \ge \left. 0 \right\}$$
C
$$\left\{ {{a^m}{b^n}|m \ge 0\,\,\,\,} \right.$$ or $$\,\,\,\,n > \left. 0 \right\}\,\,\,\,$$ and $$\left\{ {{a^m}{b^n}|m > 0\,\,\,\,} \right.\,$$ and $$\,\,\,\,n > \left. 0 \right\}\,\,\,\,$$
D
$$\left\{ {{a^m}{b^n}|m \ge 0\,\,\,\,} \right.$$ and $$\,\,\,n > \left. 0 \right\}\,\,\,\,$$ and $$\left\{ {{a^m}{b^n}|m > 0\,\,\,\,} \right.\,$$ or $$\,\,\,\,n > \left. 0 \right\}\,\,\,\,$$
GATE CSE Subjects
Software Engineering
Web Technologies
EXAM MAP
Medical
NEETAIIMS
Graduate Aptitude Test in Engineering
GATE CSEGATE ECEGATE EEGATE MEGATE CEGATE PIGATE IN
Civil Services
UPSC Civil Service
Defence
NDA
Staff Selection Commission
SSC CGL Tier I
CBSE
Class 12