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MiSawa/gist:3931689

Created October 22, 2012 14:12
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PE problem 0092
Raw
gistfile1.rb
#!/usr/bin/ruby
def f(n)
n.to_s.split('').map(&:to_i).inject(0){|a,b|a+b**2}
end
a = Hash.new do |hash, n|
hash[n] = (n == 1 || n == 89) ? n : hash[f(n)]
end
p 1.upto(1E7).count{|n|a[f(n)] == 89}
#=> 8581146
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