Pushdown Automaton: CFL and the pumping lemma
Pushdown Automaton: CFL and the pumping lemma
Pushdown Automaton: CFL and the pumping lemma
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From PDA to CFG<br />
Option 1: The stack also empty in <strong>the</strong> middle<br />
• If <strong>the</strong> stack become empty at some state r <strong>the</strong>n <strong>the</strong><br />
word wL pq can be reconstructed by a<br />
concatenation of a word from L pr <strong>and</strong> a word from<br />
L rq , thus L pr L rq L pq<br />
• In <strong>the</strong> CFG we express this by a rule: A pq A pr A rq<br />
p<br />
r<br />
q<br />
generated by A pr<br />
generated by A rq<br />
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