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Euler problems/161 to 170

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== [http://projecteuler.net/index.php?section=problems&id=161 Problem 161] ==
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Do them on your own!
Triominoes
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Solution:
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<haskell>
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problem_161 = undefined
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</haskell>
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== [http://projecteuler.net/index.php?section=problems&id=162 Problem 162] ==
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Hexadecimal numbers
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Solution:
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<haskell>
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problem_162 = undefined
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</haskell>
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== [http://projecteuler.net/index.php?section=problems&id=163 Problem 163] ==
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Cross-hatched triangles
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Solution:
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<haskell>
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problem_163 = undefined
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</haskell>
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== [http://projecteuler.net/index.php?section=problems&id=164 Problem 164] ==
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Numbers for which no three consecutive digits have a sum greater than a given value.
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Solution:
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<haskell>
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addDigit x = [[sum [x !! b !! c | c <- [0..9-a-b]] | b <- [0..9-a]] | a<-[0..9]]
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x3 = [[10-a-b | b <- [0..9-a]] | a <- [0..9]]
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x20 = iterate addDigit x3 !! 17
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problem_164 = sum [x20 !! a !! b | a <- [1..9], b <- [0..9-a]]
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</haskell>
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== [http://projecteuler.net/index.php?section=problems&id=165 Problem 165] ==
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Intersections
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Solution:
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<haskell>
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problem_165 = undefined
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</haskell>
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== [http://projecteuler.net/index.php?section=problems&id=166 Problem 166] ==
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Criss Cross
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Solution:
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<haskell>
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problem_166 =
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    sum [ product (map count [[0, c, b-d, a-b-d],
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            [0, b-a, c+d-a, b+d-a],
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            [0, -b-c, a-b-c-d, -c-d],
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            [0, a, d, c+d]])|
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        a <- [-9..9],
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        b <- [-9+a..9+a],
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        c <- [-9..9],
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        d <- [-9+a-c..9+a-c]]
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    where
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    count xs
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        |u<l=0
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        |otherwise=u-l+1
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        where
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        l = -minimum xs
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        u = 9-maximum xs
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</haskell>
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== [http://projecteuler.net/index.php?section=problems&id=167 Problem 167] ==
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Investigating Ulam sequences
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Solution:
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<haskell>
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problem_167 = undefined
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</haskell>
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== [http://projecteuler.net/index.php?section=problems&id=168 Problem 168] ==
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Number Rotations
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Solution:
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<haskell>
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problem_168 = undefined
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</haskell>
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== [http://projecteuler.net/index.php?section=problems&id=169 Problem 169] ==
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Exploring 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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problem_169 = undefined
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</haskell>
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== [http://projecteuler.net/index.php?section=problems&id=170 Problem 170] ==
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Find the largest 0 to 9 pandigital that can be formed by concatenating products.
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Solution:
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<haskell>
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problem_170 = undefined
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</haskell>
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Revision as of 21:43, 29 January 2008

Do them on your own!