Find longest palindrome substring, Microsoft Coding Competition 2014 https://github.com/Tomdarling/Microsoft-Competition/tree/master/bin/palindromePhrases

findpalindrome.rb

require 'awesome_print'
matchstr = /[[:punct:]]|[[:space:]]|[^[:ascii:]]/

class String
  def palindrome?
    self == self.reverse
  end
end

class Array
  # This returns all combinations of each slice. each_slice normally returns:
  #   ["A","B","C","D"] => ["A","B"], ["C","D"] 
  # but here:
  #   ["A","B","C","D"] => ["A","B"], ["B",C"], ["C","D"] 
  def each_slice_exhaustive( size )
    Enumerator.new do |enum|
      last = []

      if size == self.size
        enum.yield self.join('')
      end

      self.each do |c|
      if last.size < size 
          last << c
          next
        end

        last << c
        enum.yield last.join('') #eh, speeds things up to do it now, also fixes shallow copy problems
        last.shift
      end
    end
  end
end

def arrayFind( contents )
  contents.each do |l|
    print "\nString #", contents.index(l) + 1, ":\n"
    found = false
    l.size.downto(2) do |i|
      break if found
      if i != l.size
        print "\b"*6
      end
      print (100-(i.to_f/l.size*100)).round(1), "%"
      l.chars.each_slice_exhaustive(i).each do |slice|
        if slice.palindrome?
          $palindromes << slice
          found = true
          break
        end
      end
    end
  end
end

def sliceFind( contents )
  contents.each do |l|
    found = false
    l.size.downto(2) do |i|
      break if found
      # create string slices of size i from index j
      0.upto(l.size-i) do |j|
        w = l.slice(j,i)
        if w.palindrome?
          found = true
          $palindromes << w
          break
        end
      end
    end
  end
end



contents = []
original = []
File.open(ARGV[0], 'r') do |f|
  f.each_line do |line|
    contents << line.gsub( matchstr, '' ).downcase
    original << line
  end
end

$palindromes = []


if ARGV[1] == "array" 
  print "Array find: \n"
  arrayFind( contents )
else
  print "Slice find: \n"
  sliceFind( contents )
end

$palindromes.map { |p| print p, "\n" }
print "\n"

# Now relate our palindrome to the source text
$palindromes.each do |p|
  match = []
  palini = 0
  # go through source string until, ignoring removed characters, we find our palindrome
  # where the longest is aabaa
  original[$palindromes.index p].chars.each do |o|
    if o =~ matchstr
      match << o if palini > 0
      next
    end

    if p[palini] == o.downcase
      matching = true
      palini += 1
      match << o
    else
      matching = false
      match = []
      palini = 0
    end

    if palini == p.length
      print match.join(''), "\n"
      break
    end
  end
end