20 lines
509 B
Haskell
20 lines
509 B
Haskell
-- n! means n × (n − 1) × ... × 3 × 2 × 1
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--
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-- For example, 10! = 10 × 9 × ... × 3 × 2 × 1 = 3628800,
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-- and the sum of the digits in the number 10! is 3 + 6 + 2 + 8 + 8 + 0 + 0 = 27.
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--
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-- Find the sum of the digits in the number 100!
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import ProjectEuler (digitSum)
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factorial :: (Integral a) => a -> a
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factorial 0 = 1
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factorial n = n * factorial (n - 1)
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main = do
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let result = digitSum $ factorial 100
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putStrLn $
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"Project Euler, Problem 20\n"
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++ "Answer: "
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++ show result
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