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  1. pathCount :: [[Bool]] -> Int
  2. pathCount matrix = count (0,0)
  3.   where
  4.     n = length matrix - 1
  5.     count (i,j) = if i == n && j == n then 1 else a + b
  6.       where
  7.         a = if j == n || ((matrix !! i) !! (j+1)) then 0 else count (i, j + 1)
  8.         b = if i == n || ((matrix !! (i+1)) !! j) then 0 else count (i + 1, j)
  9.  
  10. testMatrix1 :: [[Bool]]
  11. -- ...
  12. -- .#.
  13. -- ...
  14. testMatrix1 = [[ False, False, False ],[ False, True, False ],[ False, False, False ]]
  15. testMatrix2 = map (map (== '#')) [
  16.   ".#..",
  17.   "...#",
  18.   ".#..",
  19.   "...."
  20.   ]
  21. testMatrix3 = map (map (== '#')) [
  22.   "..#.",
  23.   "..#.",
  24.   "....",
  25.   ".##."
  26.   ]
  27.  
  28. main = do
  29.   print (pathCount testMatrix1) -- 2
  30.   print (pathCount testMatrix2) -- 3
  31.   print (pathCount testMatrix3) -- 3
  32.  
Success #stdin #stdout 0s 4520KB
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https://ideone.com/hFzcYM
language:
Haskell (ghc 8.4.4)
created:
6 years ago
visibility:
public

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