Question

I have a variable containing a string like this in Ruby 1.9.3

#HELLO
#HELLO
#HELLO
#HELLO
#WORLD
#WORLD
#WORLD
#WORLD
#FOO
#BAR
#WORLD

I’d like it to be transformed to something like :

4 times #HELLO end
4 times #WORLD end
#FOO
#BAR
#WORLD

That’s to say, I’d like consecutive duplicate strings to be grouped into one with the amount aside.

Is there a clever way of doing this using Ruby’s functional programming power or other techniques ?

Answer 1

Try this:

str = "#HELLO
#HELLO
#HELLO
#HELLO
#WORLD
#WORLD
#WORLD
#WORLD
#FOO
#BAR
#WORLD"

result = ""
identical_lines = 1
str << "\n " # we need a last line to compare

str.lines.each_cons(2) do |line1,line2|
  if line1 == line2
    identical_lines += 1
  elsif identical_lines > 1
    result << "#{identical_lines} times #{line1.chomp} end\n"
    identical_lines = 1
  else
    result << line1
  end
end

puts result

This program outputs

4 times #HELLO end
4 times #WORLD end
#FOO
#BAR
#WORLD