Euler18.hs

first (x,_,_) = x
second (_,x,_) = x
third (_,_,x) = x


triangle = 
  [
  [75],
  [95,64],
  [17,47,82],
  [18,35,87,10],
  [20,04,82,47,65],
  [19,01,23,75,03,34],
  [88,02,77,73,07,63,67],
  [99,65,04,28,06,16,70,92],
  [41,41,26,56,83,40,80,70,33],
  [41,48,72,33,47,32,37,16,94,29],
  [53,71,44,65,25,43,91,52,97,51,14],
  [70,11,33,28,77,73,17,78,39,68,17,57],
  [91,71,52,38,17,14,91,43,58,50,27,29,48],
  [63,66,04,68,89,53,67,30,73,16,69,87,40,31],
  [04,62,98,27,23,09,70,98,73,93,38,53,60,04,23]
  ]
  
rows = length triangle

generateTuples :: [Integer] -> [Integer] -> [(Integer,Integer,Integer)]
generateTuples listA listB = zip3 listA listB (tail listB)
--Returns a list of tuples in format (Node,Child,Child)
--Example: generateTuples (triangle !! 1) (triangle !! 2) will return [(95,17,47),(64,47,82)]

tuplesToSum :: [(Integer,Integer,Integer)] -> [Integer]
tuplesToSum list = map (\x -> first x + (max (second x) (third x))) list

addMaxChild listA listB = tuplesToSum (generateTuples listA listB)

triangleMaxPath n = 
  if n==14 then (triangle !! n)
  else addMaxChild (triangle !! n) (triangleMaxPath (n+1))