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UGC-NET | UGC NET CS 2015 Jun – III | Question 63

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Given the following grammars: 
G1: S → AB|aaB 
A → aA | ∈ 
B → bB | ∈ 
G2: S → A|B 
A → aAb | ab 
B → abB | ∈ 

Which of the following is correct?

(A)

G 1 is ambiguous and G 2 is unambiguous grammars

(B)

G 1 is unambiguous and G 2 is ambiguous grammars

(C)

both G 1 and G 2 are ambiguous grammars

(D)

both G 1 and G 2 are unambiguous grammars


Answer: (C)

Explanation:

G1: S → AB|aaB 
A → aA | ∈ 
B → bB | ∈
Let\’s generate aab 
S → aaB 
S → aabB 
S → aab. one way 
S → AB 
S → aAB 
S → aaAB 
S → aaB 
S → aabB 
S → aab another way. 
G1 is ambiguous because we can generate same string by two different ways. 
G2: S → A|B 
A → aAb | ab 
B → abB | ∈ 
Let\’s generate ab. 
S → A 
A → aAb 
A → ab. One way. 
S → B 
B → abB 
B → ab. another way. 
G2 is ambiguous because we can generate same string by two different ways. 

So, option (C) is correct.


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Last Updated : 10 Nov, 2022
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