Difference between revisions of "Talk:Euler problems/1 to 10"
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The solution for problem 7 has an off-by-one error, no? Doesn't (!!) start indexing at 0? |
The solution for problem 7 has an off-by-one error, no? Doesn't (!!) start indexing at 0? |
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+ | The solution for problem 8 is not generic and requires check the last digits. |
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+ | Below shows the problem and suggested correction for groupsOf. |
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+ | <haskell> |
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+ | groupsOf _ [] = [] |
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+ | groupsOf n xs = |
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+ | take n xs : groupsOf n ( tail xs ) |
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+ | |||
+ | groupsOf' n xs |
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+ | | length group < n = [] |
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+ | | otherwise = group : groupsOf' n ( tail xs ) |
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+ | where group = take n xs |
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+ | |||
+ | digits = [1,1,1,0,9,9] |
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+ | |||
+ | max3 = maximum $ map product $ groupsOf 3 digits -- 81 (wrong) |
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+ | max3' = maximum $ map product $ groupsOf' 3 digits -- 1 (correct) |
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+ | </haskell> |
Revision as of 15:12, 7 January 2009
Should the "solution" of problem 10 not contain a way how the primes are constructed? In itself its no solution. hk
- It's in problem 3 earlier on the page. The primes function is needed for the solution of many problems. Quale 16:55, 26 February 2008 (UTC)
- It's barely a solution anyway, IMHO. They've changed the problems to all primes below *two* million now, and it takes about 3 minutes to run for me (Athlon64 3200+). Exscape 18:29, 27 May 2008 (UTC)
The solution for problem 7 has an off-by-one error, no? Doesn't (!!) start indexing at 0?
The solution for problem 8 is not generic and requires check the last digits.
Below shows the problem and suggested correction for groupsOf.
groupsOf _ [] = []
groupsOf n xs =
take n xs : groupsOf n ( tail xs )
groupsOf' n xs
| length group < n = []
| otherwise = group : groupsOf' n ( tail xs )
where group = take n xs
digits = [1,1,1,0,9,9]
max3 = maximum $ map product $ groupsOf 3 digits -- 81 (wrong)
max3' = maximum $ map product $ groupsOf' 3 digits -- 1 (correct)