Ullman (Compiler Design) Edition 2 Exercise 2.2 Question 3 (Page No. 51)

Question

 Which of the grammars are ambiguous? 

1. $S\rightarrow 0S1 \mid 01$
2. $S\rightarrow +SS \mid -SS \mid a$
3. $S\rightarrow S(S)S \mid \epsilon$
4. $S\rightarrow aSbS \mid bSaS \mid \epsilon$
5. $S\rightarrow a \mid S+S \mid SS \mid S^{\ast} \mid (S)$

Answer 1

OPTION A,B,D-We can easily say its not ambiguous on the basis of observation.

OPTION C- Getting 2 different parse trees for the string { () () }. 

OPTION E- Getting 2 different parse trees for {a+a+a}.

So answer should be C and E.

correct me if m wrong (:

 

Answer 2

C.

option c can have two parse tree for same string, {  () ()   } thats why it is ambigious,