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The nth term of the sequence of triangle numbers is given by, tn = ½n(n+1); so the first ten triangle numbers are:

1, 3, 6, 10, 15, 21, 28, 36, 45, 55, ...

By converting each letter in a word to a number corresponding to its alphabetical position and adding these values we form a word value. For example, the word value for SKY is 19 + 11 + 25 = 55 = t10. If the word value is a triangle number then we shall call the word a triangle word.

Using words.txt (right click and 'Save Link/Target As...'), a 16K text file containing nearly two-thousand common English words, how many are triangle words?
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using DelimitedFiles

function calc()
  x = sort!(vec(readdlm(dirname(@__FILE__()) * "/../Resources/p42.txt", ',', AbstractString)))
  tn = [div(n*(n+1),2) for n in 1:100]
  trianglewords = 0
  for element in x
    wordsum = 0
    for character in element
      wordsum += Int(character)-64
    end
    trianglewords += in(wordsum, tn) == true ? 1 : 0
  end
  trianglewords
end
@time println(calc())
