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Haskell Quiz/Maximum Sub-Array/Solution Kristof

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< Haskell Quiz | Maximum Sub-Array(Difference between revisions)
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Revision as of 19:47, 11 August 2007

This solution uses a left fold to find the maximum sum. It keeps track of the maximum sublist found so far (the list
max
and it's sum
sum
), and the maximum sublist that contains the current number (
r
and
rsum
).
max_sublist l = reverse $ fst $ foldl find_max ([],(0,[],0)) l where
  find_max (max, (sum, r, rsum)) x = (max', (sum', r', rsum'))
    where
    (r', rsum')  = if (rsum > 0)
                   then (x:r, rsum+x)
                   else ([x], x)
    (max', sum') = if (rsum' > sum)
                   then (r', rsum')
                   else (max, sum)