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  1. def pda_accept(string):
  2.     stack = []
  3.     for char in string:
  4.         if char == 'a':
  5.             stack.append('a')
  6.         elif char == 'b':
  7.             if len(stack) == 0 or stack[-1] != 'a':
  8.                 return False
  9.             stack.pop()
  10.     return len(stack) == 0
  11.  
  12. print(pda_accept("ab")) # True
  13. print(pda_accept("aabb")) # True
  14. print(pda_accept("aab")) # False
Success #stdin #stdout #stderr 0.02s 6904KB
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Standard input is empty
stdout
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Standard output is empty
stderr
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ERROR: /home/RAK7XU/prog:14:31: Syntax error: Unexpected end of file
ERROR: '$runtoplevel'/0: Undefined procedure: program/0
   Exception: (3) program ? EOF: exit
https://ideone.com/GZKyqy
language:
Prolog (swi 7.6.4)
created:
1 year ago
visibility:
public

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