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@flanger001
Created May 27, 2015 20:18
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Kaprekar number
# https://rubymonk.com/learning/books/1-ruby-primer/problems/150-kaprekar-s-number
def kaprekar?(k)
k_st = k.to_s
kk = k**2
kk_st = kk.to_s
offset_length = kk.to_s.length.odd? ? k_st.length - 1 : k_st.length
left = kk_st[0, offset_length]
right = kk_st[offset_length, k_st.length]
k == left.to_i + right.to_i
end
numbers = [9, 46, 55, 90, 297, 703]
vals = [true, false, true, false, true, true]
vals == numbers.map { |n| kaprekar?(n) }
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