Talk:Euler problems/1 to 10: Difference between revisions
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(Discussing alternative solution to problem 8) |
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max5' = maximum $ map product $ groupsOf' 5 digits -- 1 (correct) | max5' = maximum $ map product $ groupsOf' 5 digits -- 1 (correct) | ||
</haskell> | </haskell> | ||
:Why not use <hask>tails</hask> and pattern matching like below? | |||
:<haskell>maximum [product xs | xs@[_,_,_,_,_] <- map (take 5) (tails digits)]</haskell> | |||
:-- [[User:RayNbow|RayNbow]] 22:08, 24 January 2010 (UTC) | |||
Revision as of 22:08, 24 January 2010
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 = [1,1,1,1,1,0,9,9,9,9]
max5 = maximum $ map product $ groupsOf 5 digits -- 6561 (wrong)
max5' = maximum $ map product $ groupsOf' 5 digits -- 1 (correct)- Why not use
tailsand pattern matching like below? maximum [product xs | xs@[_,_,_,_,_] <- map (take 5) (tails digits)]
- -- RayNbow 22:08, 24 January 2010 (UTC)