Find the longest palindrome substring

Clay Shentrup

Jan 20, 2020·1 min read

Using Ruby…

def longest(string)
  string.length.downto(2) do |pal_length|
    0.upto(string.length - pal_length) do |index|
      pal = string[index, pal_length]
      return pal if is_pal?(pal)
    end
  end
  1
enddef is_pal?(string)
  0.upto(string.length / 2.0) do |i|
    return false if string[i] != string[string.length - i - 1]
  end
  true
endputs longest("foofi") # "foof"
puts longest("boyob") # "boyob"
puts longest("lallal") # "lallal"