Cracking the Code Interview, Exercise 1.5

Ex0105.rb

#!/usr/bin/env ruby

module Ex0105
    def self.compress(str)
        out = str.scan(/./).reduce([[], 't', 0]) do |(buf, cur, num), c|
            if cur == c
                [buf, cur, num + 1]
            else
                if num > 0
                    buf << cur
                    buf << num.to_s
                end
                [buf, c, 1]
            end
        end.join
    
        if out.size < str.size
            out
        else
            str
        end
    end
end 

if __FILE__ == $0
    for test in %w[a aaa aaaaaaaaaaac abc aabcccccaa] + [""]
        puts "compress('#{test}'): '#{Ex0105.compress(test)}'"
    end
end