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  1. f = -> n {
  2.   (0..n).lazy.map {|i| [n - i, n + i].select {|x| x.to_s.reverse.to_i == x}}.find(&:any?).uniq
  3. }
  4. p [0, 17, 100].map {|n| [n, f.(n)]}
  5.  
Success #stdin #stdout 0.01s 8012KB
comments (?)
stdin 
Standard input is empty
stdout 
[[0, [0]], [17, [22]], [100, [99, 101]]]
https://ideone.com/N0w91j
language:
Ruby (ruby 2.5.5)
created:
92 days ago
visibility:
secret

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