ar = %w(1001110011
1110111011
0010010010
1010101010
1111111111
0100101101
0100100
101
11
00
1)
ar.each do |str|
rep_pos = (str.size/2).downto(1).find{|pos| str.start_with? str[pos..-1]}
puts str, rep_pos ? " "*rep_pos + str[0, rep_pos] : "(no repetition)", ""
end