CDE

Task/Dinesmans-multiple-dwelling-problem/Haskell/dinesmans-multiple-dwelling-problem-1.hs

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+import Data.List (permutations)
+import Control.Monad (guard)
+
+dinesman :: [(Int,Int,Int,Int,Int)]
+dinesman = do
+  -- baker, cooper, fletcher, miller, smith are integers representing
+  -- the floor that each person lives on, from 1 to 5
+
+  -- Baker, Cooper, Fletcher, Miller, and Smith live on different floors
+  -- of an apartment house that contains only five floors.
+  [baker, cooper, fletcher, miller, smith] <- permutations [1..5]
+
+  -- Baker does not live on the top floor.
+  guard $ baker /= 5
+
+  -- Cooper does not live on the bottom floor.
+  guard $ cooper /= 1
+
+  -- Fletcher does not live on either the top or the bottom floor.
+  guard $ fletcher /= 5 && fletcher /= 1
+
+  -- Miller lives on a higher floor than does Cooper.
+  guard $ miller > cooper
+
+  -- Smith does not live on a floor adjacent to Fletcher's.
+  guard $ abs (smith - fletcher) /= 1
+
+  -- Fletcher does not live on a floor adjacent to Cooper's.
+  guard $ abs (fletcher - cooper) /= 1
+
+  -- Where does everyone live?
+  return (baker, cooper, fletcher, miller, smith)
+
+main :: IO ()
+main = do
+  print $ head dinesman -- print first solution: (3,2,4,5,1)
+  print dinesman -- print all solutions (only one): [(3,2,4,5,1)]

Task/Dinesmans-multiple-dwelling-problem/Haskell/dinesmans-multiple-dwelling-problem-2.hs

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+import Data.List (permutations)
+main = print [ (b,c,f,m,s) | [b,c,f,m,s] <- permutations [1..5], b/=5,c/=1,f/=1,f/=5,m>c,abs(s-f)>1,abs(c-f)>1]