ISRO CSE 2020 | Question: 60

Question

A given grammar is called ambiguous if

• A. two or more productions have the same non-terminal on the left hand side
• B. a derivation tree has more than one associated sentence
• C. there is a sentence with more than one derivation tree corresponding to it
• D. brackets are not present in the grammar

Comments

A grammar is ambiguous if and only if a sentence have two or more derivation trees so option C is correct

Answer 1

$\underline{\mathbf{Answer:}\Rightarrow}\;\mathbf{c.}$

A grammar is said to be ambigous if there exists more than one derivation tree of the given grammar, i.e., more than one LMD or RMD.

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https://www.geeksforgeeks.org/ambiguous-grammar/

Answer 2

A grammar is said to be ambiguous if it can produce more than one parse tree for a particular sentence; this occurs when two different sequences of leftmost (or rightmost) derivations can produce the same sentence from the same start symbol.

Reference:

• https://cs.uwaterloo.ca/~cbruni/CS241Resources/lectures/2019_Winter/CS241L10_cfg_ambiguity_top_down_parsing_post.pdf
• https://www.cas.mcmaster.ca/~zucker/2f/2fno/5b.pdf
• https://www.d.umn.edu/~rmaclin/cs5641/Notes/Lecture6.pdf
• https://www.univ-orleans.fr/lifo/Members/Mirian.Halfeld/Cours/TLComp/res2-CG.pdf

So, the correct answer is $(C).$ 

Comments

@Lakshman Bhaiya bhaiya the reference slide link is not working, can you please resend if possible, or any other standard source regarding different definition of ambiguity. 

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@AniMan_7 I have updated the links. 

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thanks a lot bhaiya.

Answer 3

option C

for a string it has more than one parse tree

Answer 4

option C) is the correct answer, A grammar is said to be ambiguous if for a string it is having more than one parse tree.