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Top-Down PDA

Top-Down PDA. Sequence of steps to which string X= [][[][]] has to be accepted by NPDA NT(G) Grammar has productions s [S]S|^. We compare the moves made by NT(G) in accepting this string be leftmost derivation of this string. S=> [S]S =>[ ] S => [ ][S]S => [ ][ [S] S ] S

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Top-Down PDA

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  1. Top-Down PDA Sequence of steps to which string X= [][[][]] has to be accepted by NPDA NT(G) Grammar has productions s[S]S|^

  2. We compare the moves made by NT(G) in accepting this string be leftmost derivation of this string. • S=> [S]S =>[ ] S • => [ ][S]S • => [ ][ [S] S ] S • =>[ ] [[ ] S] S • => [ ] [ [ ] [S] S] S • [ ] [ [ ] [ ] S] S • [ ] [ [ ] [ ] ] S • => [ ] [ [ ] [ ] ]

  3. Transition table for Top Down PDA NT(G)

  4. To the right of the each move that replace a variable on stack , we show the corresponding step in the left most derivation. (q0, [ ] [ [ ] [ ] ] , Z0 ) Steps are derived by using the moves in transition table |- (q1, [ ] [ [ ][ ] ], SZ0) S |- (q1, [ ] [ [ ] [ ] ] , [S]SZ0) => [S]S |- (q1, ] [ [ ] [ ] ], S]SZ0) |- (q1 , ] [ [ ] [ ] ], ]SZ0) |- (q1 , [ [ ] [ ] ], SZ0) |- (q1 , [ [ ] [ ] ], [S]SZ0) =>[ ] [S]S |- (q1 , [ ] [ ] ], S]SZ0) |- (q1, , [ ] [ ] ], [S] S]SZ0) =>[ ] [ [S]S]S |- (q1 , ] [ ] ], S] S]SZ0) |- (q1 , ] [ ] ], ] S]SZ0) |- (q1 , [ ] ], S]SZ0) |- (q1 , [ ] ], [S]S]SZ0) => [ ] [ [ ] [S]S]S |- (q1 , ] ], S]S]SZ0) |- (q1 , ] ], ]S]SZ0)

  5. |- (q1 , ], S]SZ0) |- (q1 , ], ]SZ0) |- (q1 , ^ , SZ0) |- (q1 , ^, Z0) = > [ ] [ [ ] [ ] ] |- (q2, ^ , Z0) These are the sequence of steps that string x to be accepted

  6. Thank you

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