UGC NET Computer Science July 2018 - II Question 36

Question 36

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Consider the following two Grammars :

G1 : S → SbS|a
G2 : S → aB|ab, A→GAB|a, B→ABb|b

Which of the following option is correct ?

Options:

1. (1) Only G1 is ambiguous
2. (2) Only G2 is ambiguous
3. (3) Both G1 and G2 are ambiguous
4. (4) Both G1 and G2 are not ambiguous

Answer : (3) Both G1 and G2 are ambiguous

Explanation Question 36

Solution:

Both G1 and G2 are ambiguous
As both grammars have two derivations for same string:

G1 : S → SbS|a

Grammer G1 Derivation-1:
S → SbS
        SbSbS
        ababa

Grammer G1 Derivation-2:
S → SbS
SbSbS
ababa


G2 : S → aB|ab, A→AB|a, B→ABb|b

Grammer G2 Derivation-1:
 S → aB
aABb
aABBb
aABABbb
aababbb

Grammer G2 Derivation-2:
S → aB
aABb
aAABbb
aABABbb
aababbb

Both G1 and G2 are ambiguous as both grammars have two derivations for same string as shown in above.

So, Option (3) is correct answer.

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