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I have the following grammar defined:

S -> A|B, A -> aAb | ab, B -> aBb | epsilon;

After working for some time, I still couldn't find a string to construct a distinctive parse tree to show that this grammar is ambiguous. Like: aaabbb,abab,etc. It seemed like this grammar is unambiguous. Any help?

zihaow
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1 Answers1

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This grammar is ambiguous. The string aabb can be derived in two different ways: 

S => A => aAb => aabb
S => B => aBb => aaBbb => aabb
MNos
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