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Revision as of 01:55, 31 January 2014

Let Σ = {a, b, c}. Which of the following statements is true ?

a)For any A ⊆ Σ*, if A is regular, then so is {xx | x ∊ A}

b)For any A ⊆ Σ*, if A is regular, then so is {x | xx ∊ A}

c)For any A ⊆ Σ*, if A is context-free, then so is {xx | x ∊ A}

d)For any A ⊆ Σ*, if A is context-free, then so is {x | xx ∊ A}

Solution

We can get a DFA for L as follows: Take DFA for A. Let S be its start state. For each state D of A, consider 2 separate DFAs, one with S as the start state and D as the final state and another with D as the start state and final state in final states of A. If both these DFAs accept same language make D as final state.

This procedure works as the equivalence of 2 DFAs is decidable.









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Let Σ = {a, b, c}. Which of the following statements is true ?

a)For any A ⊆ Σ*, if A is regular, then so is {xx | x ∊ A}

b)For any A ⊆ Σ*, if A is regular, then so is {x | xx ∊ A}

c)For any A ⊆ Σ*, if A is context-free, then so is {xx | x ∊ A}

d)For any A ⊆ Σ*, if A is context-free, then so is {x | xx ∊ A}

Solution[edit]

We can get a DFA for L as follows: Take DFA for A. Let S be its start state. For each state D of A, consider 2 separate DFAs, one with S as the start state and D as the final state and another with D as the start state and final state in final states of A. If both these DFAs accept same language make D as final state.

This procedure works as the equivalence of 2 DFAs is decidable.









blog comments powered by Disqus