Which of the following grammars is (are) ambiguous?

(A) s → ss | asb | bsa | λ

(B) s → asbs | bsas | λ

(C) s → aAB

A → bBb

B →  A | λ where λ denotes empty string

Choose the correct answer from the options given below:

This question was previously asked in
UGC NET Computer Science (Paper 2) 2020 Official Paper
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  1. (A) and (C) only
  2. (B)only 
  3. (B) and (C) only
  4. (A) (B) and (C)

Answer (Detailed Solution Below)

Option 4 : (A) (B) and (C)
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UGC NET Paper 1: Held on 21st August 2024 Shift 1
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Detailed Solution

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The correct answer is option 4.

Key Points

A is ambiguous because λ can be generated using leftmost derivation having two different parse trees with an empty string.

F1 Shraddha Raju 03.04.2021 D26

B is ambiguous grammar with string abab.

F1 Shraddha Raju 03.04.2021 D27

C is an ambiguous grammar with string abbbb.

F1 Shraddha Raju 03.04.2021 D28

∴ Hence the correct answer is (A) (B) and (C).

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