GATE CSE 2017 Set 1 | Question: 17

Question

Consider the following grammar:

• $P\rightarrow xQRS$
• $Q\rightarrow yz\mid z$
• $R\rightarrow w\mid \varepsilon$
• $S\rightarrow y$

What is FOLLOW($Q$)?

• A. $\left \{ R \right \}$              
• B. $\left \{ w \right \}$                
• C. $\left \{ w,y \right \}$                   
• D. $\left \{ w,\$ \right \}$

Answer 1

Follow of $Q$ is first of $R$ so we get $\{w\}$

but since $R$ can be Null so we have to check first of $S$ which is $\{y\}$

so FOLLOW $Q=\{w,y\}$

Correct option (C)

Answer 2

correct option is c.

Comments

could u plz tell me how to insert a picture in this

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Nice explanation. From this answer Follow set find rules can be verified.

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Nice Explanation :)

Answer 3

	First	Follow
P	{x}	{$}
Q	{y,z}	{w,y}
R	{w,ε}	{y}
S	{y}	{$}

Ans: (C) - {w,y}

Answer 4

so C is ans.