palindrome.rb

#Time limit exceeded
class Palindrome

  def compute(value)
    @input_array = value
    @size = @input_array.size
    @even = @size % 2 == 0
    if @even
      @pos1 = (@size/2)-1
      @pos2 = @pos1+1
    else
      @pos1 = (((@size+1)/2)-1)
      @pos2 = @pos1
    end
    @mirrored = @input_array[0..@pos1]
    @start = @even ? @pos1 : @pos2-1
    @start.downto(0) do |i|
      @mirrored << @input_array[i]
    end
    if @mirrored.join.to_i <= value.join.to_i
      nxt(@pos1, @pos2)
    end
    @mirrored.join;
  end
  def nxt(pos1, pos2)
    if pos1 < 0
      @mirrored[@size-1] = 1
      @mirrored.unshift(1)
    else 
      if @mirrored[pos1] < 9
        @mirrored[pos1] = @mirrored[pos2] = @mirrored[pos1] + 1
      else
        @mirrored[pos1] = @mirrored[pos2] = 0
        nxt(pos1-1, pos2+1)
      end
    end
  end

end

t = gets.to_i
p = Palindrome.new
1.upto(t) do |z|
  k = STDIN.bytes.map { |c| c-48}
  k = k[0...-1]
  puts p.compute(k)
end