title: Project Euler #18 in Haskell
body: <p>I am currently learning functional programming and Haskell coming from a python background. To help me learn, I decided to do some project euler problems (<a href="http://projecteuler.net/problem=18" rel="nofollow">http://projecteuler.net/problem=18</a>). Currently I am on #18. Starting with this string, </p>
  
  <pre><code>"75
  95 64
  17 47 82
  18 35 87 10
  20 04 82 47 65
  19 01 23 75 03 34
  88 02 77 73 07 63 67
  99 65 04 28 06 16 70 92
  41 41 26 56 83 40 80 70 33
  41 48 72 33 47 32 37 16 94 29
  53 71 44 65 25 43 91 52 97 51 14
  70 11 33 28 77 73 17 78 39 68 17 57
  91 71 52 38 17 14 91 43 58 50 27 29 48
  63 66 04 68 89 53 67 30 73 16 69 87 40 31
  04 62 98 27 23 09 70 98 73 93 38 53 60 04 23"
  </code></pre>
  
  <p>I managed to convert it into a nested array using this function:</p>
  
  <pre><code>map (\x -&gt; map (\y -&gt; read y :: Int) (words x)) (lines a)
  </code></pre>
  
  <p>That function outputs this:</p>
  
  <pre><code>[[75],[95,64],[17,47,82],[18,35,87,10],[20,4,82,47,65],[19,1,23,75,3,34],[88,2,77,73,7,63,67],[99,65,4,28,6,16,70,92],[41,41,26,56,83,40,80,70,33],[41,48,72,33,47,32,37,16,94,29],[53,71,44,65,25,43,91,52,97,51,14],[70,11,33,28,77,73,17,78,39,68,17,57],[91,71,52,38,17,14,91,43,58,50,27,29,48],[63,66,4,68,89,53,67,30,73,16,69,87,40,31],[4,62,98,27,23,9,70,98,73,93,38,53,60,4,23]]
  </code></pre>
  
  <ol>
  <li>Is there a way to write that conversion function without the lambdas and make
  it more readable?</li>
  <li><p>How would I convert this nested array to a tree
  structure defined like so:</p>
  
  <p>data Tree a = EmptyTree | Node a (Tree a) (Tree a) deriving (Show, Read, Eq)</p>
  
  <p>Or would it just be easier to leave it as an array and solve it from there?</p></li>
  </ol>