golf.rb

class Golf
  class << self
    def hole1 a 
      a.reduce :*
    end

    def hole2 s 
      s.split.sort_by{|i| i[1] }*' '
    end

    def hole3 i 
      hole1 1..i
    end

    def hole4 a 
      a.map { |i| i.
        sub(/(man.*)/,'hat(\1)').
        sub(/(dog.*)\)/,'\1(bone))').
        sub('cat','dead')
      }
    end

    def hole5 a 
      x = []
      a.size.times { |i| x += a.each_cons(i+1).to_a }
      x
    end

    def hole6 i 
      f="fizz"
      b="buzz"
      (1..i).map { |s|  s%15 < 1 ? f+b : s%3 < 1 ? f : s%5 < 1 ? b : s }
    end

    def hole8 i 
      a=[0,1]
      i.times { a << a[-1]+a[-2] }
      a[1..-2]
    end


    def z a
      a.group_by {|e| e[0]}
    end

    def hole9 f
      b = open(f).map {|e| e.chomp.split ', '}
      g = z b
      while (c,d = g.minmax_by {|e,s| s.size})[0][1].size*2 < b.size
        b.select {|e| e[0]==c[0]}.map &:shift
        b -= [[]]
        g = z b
      end
      d[0]
    end
  end
end

610 Characters
https://github.com/paulanthonywilson/rubygolf

602
Adding some optimisations from https://gist.github.com/987222

Hole 2 .join ' ' => _' ' (4 char)
Hole 5 (1..a.size).each => a.size.times i has to change to i+1 (2 char)
Hole 9 x < y/2.0 => x_2 < y (2 char)

600
Hole 3 (1..i) => 1..i (2 chars)

566

From https://gist.github.com/987222

 while (c,d = g.minmax_by {|e,s| s.size})[0][1].size*2 < b.size
        b.select {|e| e[0]==c[0]}.map &:shift
        b.reject! &:empty?
        g = z b
      end

Hole 9: array -= [[]] is more efficient than array.reject! &:empty? (10 chars)

x<1 is 1 less than x==0 Used 3 times (3 chars)
parenthesis not required (6 chars)
( s%15 == 0 ? f+b : ( s%3 == 0 ? f : ( s%5 == 0 ? b : s ) ) ) => s%15 < 1 ? f+b : s%3 < 1 ? f : s%5 < 1 ? b : s