Longest Palindrome Finder in Ruby

gistfile1.rb

def longest_palind(s)
    # First find all palindromes.  The way we can do
    # this is to scan through the letters searching for
    # the middle.  We can find the middle by detecting a letter
    # that meets one of two criteria- has the same letter before and after it,
    # or is the same letter.  Once we have found that it is a palindrome,
    # continue to expand the search finding the length.  Once we have the length
    # extract the string and append to the array.  Sort the array by the longest
    # and shift.
    all_pals = pals_in_str(s)
    puts all_pals.sort_by(&:length).reverse.first
end

def pals_in_str(s)
  pals = []
  len = s.length
  letters = s.scan(/./)

  letters.each_with_index do |char, index|
    if char == letters.at(index + 1)
      pals << build_pal(letters, char.dup.concat(letters.at(index + 1)), index, (index + 1))
    elsif letters.at(index - 1) == letters.at(index + 1)
      pals << build_pal(letters, char.dup, index, index)
    end
  end

  pals
end

def build_pal(letters, data, start, stop)
  steps = 0
  match = true
  while match
    steps += 1
    prev = letters.at(start - steps)
    nexxt = letters.at(stop + steps)
    match = false

    if prev == nexxt
      data.insert(0, prev)
      data.insert(-1, nexxt)
      match = true
    end
  end
  
  data
end