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Euler problems/171 to 180

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== [http://projecteuler.net/index.php?section=problems&id=171 Problem 171] ==
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Do them on your own!
Finding numbers for which the sum of the squares of the digits is a square.
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Solution:
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<haskell>
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problem_171 = undefined
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</haskell>
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== [http://projecteuler.net/index.php?section=problems&id=172 Problem 172] ==
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Investigating numbers with few repeated digits.
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Solution:
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<haskell>
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problem_172 = undefined
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</haskell>
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== [http://projecteuler.net/index.php?section=problems&id=173 Problem 173] ==
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Using up to one million tiles how many different "hollow" square laminae can be formed?
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Solution:
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<haskell>
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problem_173=
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    let c=div (10^6) 4
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        xm=floor$sqrt $fromIntegral c
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        k=[div c x|x<-[1..xm]]
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    in  sum k-(div (xm*(xm+1)) 2)
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</haskell>
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== [http://projecteuler.net/index.php?section=problems&id=174 Problem 174] ==
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Counting the number of "hollow" square laminae that can form one, two, three, ... distinct arrangements.
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Solution:
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<haskell>
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problem_174 = undefined
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</haskell>
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== [http://projecteuler.net/index.php?section=problems&id=175 Problem 175] ==
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Fractions involving the number of different ways a number can be expressed as a sum of powers of 2.
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Solution:
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<haskell>
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sternTree x 0=[]
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sternTree x y=
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    m:sternTree y n 
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    where
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    (m,n)=divMod x y
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findRat x y
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    |odd l=take (l-1) k++[last k-1,1]
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    |otherwise=k
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    where
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    k=sternTree x y
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    l=length k
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p175 x y=
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    init$foldl (++) "" [a++","|
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    a<-map show $reverse $filter (/=0)$findRat x y]
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problems_175=p175 123456789 987654321
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test=p175 13 17
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</haskell>
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== [http://projecteuler.net/index.php?section=problems&id=176 Problem 176] ==
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Rectangular triangles that share a cathetus.
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Solution:
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<haskell>
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problem_176 = undefined
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</haskell>
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== [http://projecteuler.net/index.php?section=problems&id=177 Problem 177] ==
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Integer angled Quadrilaterals.
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Solution:
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<haskell>
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problem_177 = undefined
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</haskell>
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== [http://projecteuler.net/index.php?section=problems&id=178 Problem 178] ==
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Step Numbers
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Solution:
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<haskell>
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problem_178 = undefined
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</haskell>
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== [http://projecteuler.net/index.php?section=problems&id=179 Problem 179] ==
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Consecutive positive divisors.
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Solution:
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<haskell>
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problem_179 = undefined
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</haskell>
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== [http://projecteuler.net/index.php?section=problems&id=180 Problem 180] ==
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Solution:
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<haskell>
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problem_180 = undefined
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</haskell>
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Revision as of 21:42, 29 January 2008

Do them on your own!