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3 votes
3 votes

Consider the following languages :

  1. $L_{1}=\left\{a^{k} b^{m} c^{n} \mid(k=m\right.$ or $m=n)$ and $\left.k+m+n \geq 2\right\}$
  2. $L_{2}=\left\{a^{k} b^{m} c^{n} \mid(k=m\right.$ or $m=n)$ and $\left.k+m+n \leq 2\right\}$
  3. $L_{3}=\left\{a^{k} b^{m} c^{n} \mid k+m+n \geq 2\right\}$

Which of the above languages are Regular?

  1. $\mathrm{L}_{2}$ Only
  2. $\mathrm{L}_{3}$ Only
  3. $L_{2}$ and $L_{3}$ only
  4. All
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2 Answers

6 votes
6 votes

The point to be considered here is : 

if comparison → L is NON-REGULAR,

                         → Except L is finite

 

In L1: comparison & nonfinite → Non-regular

In L2 : comparison & finite → Regular

In L3: No comparison : >= k : regular

5 votes
5 votes
In $\mathrm{L}_{1}$, there is a matching between $\mathrm{k}, \mathrm{m}$ Or $\mathrm{m}, \mathrm{n}$; so, it is Non-regular but CFL. $\mathrm{L}_{2}$ is finite, so regular. $\mathrm{L}_{3}$ is regular because No matching required.
Answer:

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