Parse trees

Question

How will we treat the given two parse trees..?  Are they same i.e one is has been derived using lmd n other using rmd or they both will be treated as two diffent parse trees concluding it as ambiguous.. Only with reference to the string 'b'  otherwise i know its ambiguous... 

Comments

For some input string when u r able to draw more than 1 parse tree that means it is ambiguous...

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Both are different tree but derived string is same.

Answer 1

In this particular grammar and string LMD and RMD both are giving the same Parse Tree, but in all cases this will not true.

A grammar is Ambiguous if there is :

1. more than one RMD  or

2. more than one LMD or

3. more than one Parse Tree for a given string

string = b gives two different parse tree. So, It is ambiguous.