20 lines
715 B
Haskell
20 lines
715 B
Haskell
-- In England the currency is made up of pound, £, and pence, p, and there are eight coins in general circulation:
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--
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-- 1p, 2p, 5p, 10p, 20p, 50p, £1 (100p) and £2 (200p)
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--
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-- How many different ways can £2 be made using any number of coins?
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import Data.Array
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import Euler
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coins = listArray (0,7) [1,2,5,10,20,50,100,200] :: Array Int Int
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nWays total = arr ! (total, snd (bounds coins))
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where
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arr = array ((0, fst (bounds coins)), (total, snd (bounds coins)))
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[ ((n, c), sum [ arr ! (n - (coins!c'), c') + if n == coins!c' then 1 else 0
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| c' <- [fst (bounds coins)..c], coins!c' <= n ])
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| n <- [0..total], c <- indices coins ]
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main = print $ nWays 200
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