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Euler problems/161 to 170

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== [http://projecteuler.net/index.php?section=problems&id=161 Problem 161] ==
+
Do them on your own!
Triominoes
 
 
Solution:
 
<haskell>
 
problem_161 = undefined
 
</haskell>
 
 
== [http://projecteuler.net/index.php?section=problems&id=162 Problem 162] ==
 
Hexadecimal numbers
 
 
Solution:
 
<haskell>
 
problem_162 = undefined
 
</haskell>
 
 
== [http://projecteuler.net/index.php?section=problems&id=163 Problem 163] ==
 
Cross-hatched triangles
 
 
Solution:
 
<haskell>
 
problem_163 = undefined
 
</haskell>
 
 
== [http://projecteuler.net/index.php?section=problems&id=164 Problem 164] ==
 
Numbers for which no three consecutive digits have a sum greater than a given value.
 
 
Solution:
 
<haskell>
 
addDigit x = [[sum [x !! b !! c | c <- [0..9-a-b]] | b <- [0..9-a]] | a<-[0..9]]
 
x3 = [[10-a-b | b <- [0..9-a]] | a <- [0..9]]
 
x20 = iterate addDigit x3 !! 17
 
problem_164 = sum [x20 !! a !! b | a <- [1..9], b <- [0..9-a]]
 
</haskell>
 
 
== [http://projecteuler.net/index.php?section=problems&id=165 Problem 165] ==
 
Intersections
 
 
Solution:
 
<haskell>
 
problem_165 = undefined
 
</haskell>
 
 
== [http://projecteuler.net/index.php?section=problems&id=166 Problem 166] ==
 
Criss Cross
 
 
Solution:
 
<haskell>
 
problem_166 =
 
sum [ product (map count [[0, c, b-d, a-b-d],
 
[0, b-a, c+d-a, b+d-a],
 
[0, -b-c, a-b-c-d, -c-d],
 
[0, a, d, c+d]])|
 
a <- [-9..9],
 
b <- [-9+a..9+a],
 
c <- [-9..9],
 
d <- [-9+a-c..9+a-c]]
 
where
 
count xs
 
|u<l=0
 
|otherwise=u-l+1
 
where
 
l = -minimum xs
 
u = 9-maximum xs
 
</haskell>
 
 
== [http://projecteuler.net/index.php?section=problems&id=167 Problem 167] ==
 
Investigating Ulam sequences
 
 
Solution:
 
<haskell>
 
problem_167 = undefined
 
</haskell>
 
 
== [http://projecteuler.net/index.php?section=problems&id=168 Problem 168] ==
 
Number Rotations
 
 
Solution:
 
<haskell>
 
problem_168 = undefined
 
</haskell>
 
 
== [http://projecteuler.net/index.php?section=problems&id=169 Problem 169] ==
 
Exploring the number of different ways a number can be expressed as a sum of powers of 2.
 
 
Solution:
 
<haskell>
 
problem_169 = undefined
 
</haskell>
 
 
== [http://projecteuler.net/index.php?section=problems&id=170 Problem 170] ==
 
Find the largest 0 to 9 pandigital that can be formed by concatenating products.
 
 
Solution:
 
<haskell>
 
problem_170 = undefined
 
</haskell>
 

Revision as of 21:43, 29 January 2008

Do them on your own!