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  1. -- http://i...content-available-to-author-only...e.com/1OIrFf
  2. import Data.List
  3. import Data.Maybe
  4. import Data.Map (keys, fromList, elems) 
  5. import Data.Map as M (lookup)
  6. checkBraces "" = True
  7. checkBraces e = checkBrace e [] where
  8. 	braceToBraceMap = fromList [('(',')'), ('{','}'), ('[',']')]
  9. 	openBraces = keys braceToBraceMap
  10. 	closeBraces = elems braceToBraceMap
  11. 	braceToBrace brace = fromJust $ M.lookup brace braceToBraceMap
  12. 	checkBrace (c:e) s | elem c openBraces = checkBrace e ((braceToBrace c):s)
  13. 	checkBrace (c:e) (h:s) | (elem c closeBraces) && (h==c) = checkBrace e s
  14. 	checkBrace (_:e) _ = False
  15. 	checkBrace "" [] = True
  16. 	checkBrace "" _ = False
  17. main = mapM_ (print . checkBraces) bracesExpressionExamples where
  18. 	bracesExpressionExamples = 
  19. 		[
  20. 			"({[{}]{}[]})",
  21. 			"({}}{[{}]{}[]})",
  22. 			"({[{}]{}[]}",
  23. 			"({[{}]{}]})",
  24. 			"({[{}{}[]})",
  25. 			"",
  26. 			"{}"
  27. 		]
Success #stdin #stdout 0s 6268KB
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stdin 
Standard input is empty
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True
False
False
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https://ideone.com/1OIrFf
language:
Haskell (ghc 8.4.4)
created:
12 years ago
visibility:
public

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