16 lines
416 B
Haskell
16 lines
416 B
Haskell
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-- Problem 63
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-- 13 February 2004
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--
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-- The 5-digit number, 16807=7^5, is also a fifth power. Similarly, the 9-digit number, 134217728=8^9, is a ninth power.
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--
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-- How many n-digit positive integers exist which are also an nth power?
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powers n = map (^n) [1..100]
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is_solution n x = (x >= 10^(n-1)) && (x < 10^n)
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find n = filter (is_solution n) (powers n)
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main = do
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print $ sum $ map (length . find) [1..100]
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