The document discusses ambiguity in context free grammars. It provides two examples of grammars that are ambiguous and shows that there are multiple leftmost derivations for strings generated by these grammars. Specifically, the grammars presented have two different leftmost derivation trees for the strings "aab" and "a+a+a" respectively, showing that the grammars are ambiguous.

1. REMOVING AMBIGUITY
FROM CFG
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2. Group Members:
1. Muradul Islam Jamil (152-35-1203)
2. Mahadi Hasan Joy (152-35-1207)
3. Mazed Mourshed (152-35-1215)
Md. Anwar Hossen
Lecturer, Dept. of Software Engineering
Daffodil International University
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3. AMBIGUITY IN CFG
If a context free grammar has more than one derivation tree
for some string, it is called an ambiguous grammar. There
exist multiple right-most or left-most derivations for some
string generated from
that grammar.
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4. PROBLEM
Check whether the grammar G with production rules −
S → AB | aaB
A → a | Aa
B → b
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5. SOLUTION
Let’s find out the derivation tree for the string “aab". It has two leftmost deriv
i) S → aaB → aab
ii) S → AB →AaB → aaB → aab
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6. ANOTHER PROBLEM
Check whether the grammar G with
production rules −
S → S + S | S * S | a
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7. SOLUTION
Let’s find out the derivation tree for the string “a+a+a". It has two leftmost d
i) S → S + S → S + S + S → a + a + S → a + a + a
ii) S → S + S → S + S + S → S + a + a → a + a + a
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8. SOLUTION
Let’s find out the derivation tree for the string “a+a*a". It has two leftmost de
i) S → S + S → a + S → a + S * S → a + a * a
ii) S → S * S → S + S * S → a + a * S → a + a * a
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9. THANK
YOU
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