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  1. def checkAB(s):
  2.     if len(s) == 0 or s[0] != 'a':
  3.         return False
  4.  
  5.     def loop(val):
  6.         if len(val) == 0:
  7.             return True
  8.         if val[0] == 'a':
  9.             return loop(val[1:])
  10.         if len(val) > 2 and val[0] == 'b' and val[1] == 'b' and val[2] == 'b':
  11.             return False
  12.         if len(val) == 1 and val[0] == 'b':
  13.             return False
  14.         if val[0] == 'b' and val[1] == 'b':
  15.             return loop(val[2:])
  16.         else:
  17.             return False
  18.     return loop(s)
  19.  
  20. strings = [
  21.     "a",
  22.     "aaa",
  23.     "abb",
  24.     "abba",
  25.     "abbabb",
  26.     "abbabba",
  27.     "aaabbaabb",
  28.     "abbabbabbaaa",
  29.     "abbaaaaabbaaaaababbbbabbababababbba"
  30.     "aba",
  31.     "baba",
  32.     "baabb",
  33.     "aabbbaa",
  34.     "abbbb",
  35.     "abbb",
  36.     "abbbbbb",
  37.     "aabbabbbb",
  38.     "aabbabbab",
  39.     "ababab",
  40.     "bba",
  41.     "ababab",
  42.     "bba",
  43.     "aaab",
  44.     "aaabbb",
  45.     "aaabbbb",
  46.     "abbbbbbb"
  47. ]
  48.  
  49. for s in strings:
  50.     print(f"{s} --> {checkAB(s)}")
  51.  
  52.  
Success #stdin #stdout 0.02s 9280KB
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stdin
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Standard input is empty
stdout
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a --> True
aaa --> True
abb --> True
abba --> True
abbabb --> True
abbabba --> True
aaabbaabb --> True
abbabbabbaaa --> True
abbaaaaabbaaaaababbbbabbababababbbaaba --> False
baba --> False
baabb --> False
aabbbaa --> False
abbbb --> False
abbb --> False
abbbbbb --> False
aabbabbbb --> False
aabbabbab --> False
ababab --> False
bba --> False
ababab --> False
bba --> False
aaab --> False
aaabbb --> False
aaabbbb --> False
abbbbbbb --> False
https://ideone.com/wvcthb
language:
Python 3 (python  3.9.5)
created:
3 years ago
visibility:
public

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