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Euler problems/171 to 180

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

Revision as of 21:42, 29 January 2008

Do them on your own!