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Unit 8 · Theory of Computation and Compilers Paper 2 CS · November 2021

Let L1 = {0ⁿ1ⁿ0ᵐ | n ≥ 1, m ≥ 1}, L2 = {0ⁿ1ᵐ0ᵐ | n ≥ 1, m ≥ 1}, L3 = {0ⁿ1ⁿ0ⁿ | n ≥ 1}. Which are correct? A. L3 = L1 ∩ L2. B. L1 and L2 are context free but L3 is not. C. L1 and L2 are not context free but L3 is. D. L1 is a subset of L3.

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Correct answer: A. A and B only

Explanation

Requiring both 0ⁿ1ⁿ and 1ᵐ0ᵐ forces all three counts equal, so L1 ∩ L2 = L3. L1 and L2 are CFLs; L3 is the classic non-CFL. So A and B.

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