gistfile1.rb

#!/usr/bin/env ruby
# Solution for a Quick Ruby Kata by Noel Rappin - 
# http://railsrx.com/2010/09/27/a-quick-ruby-kata/
# Modification of the Solution for Problem number 76 on Project Euler
# http://projecteuler.net/index.php?section=problems&id=76

class Array
  def meets_criteria?
    meets_criteria = false
    count_hash = Hash.new(0)
    self.each do |number|
      count_hash[number] += 1
    end
    max_count = 0
    count_hash.each do  |key, value|
      max_count = value if value > max_count
    end
    meets_criteria = true if max_count == 2
    meets_criteria
  end
end


start_time = Time.new

required_sum = 15
max_number = 9

combinations = [] # To find all combinations of 1-9 irrespective of the count that add up to 15

while max_number > 0
  combination_array = []
  divisor, remainder = required_sum.divmod(max_number)
  divisor.times {combination_array << max_number}
  if remainder > 0
    combination_array << remainder
  end
  combinations << Array.new(combination_array)
  while (max_number + combination_array.length - 1) < required_sum # When all items other than max_number are 1
    total = 0
    to_reduce = combination_array.pop
    total += to_reduce
    while to_reduce == 1
      to_reduce = combination_array.pop
      total += to_reduce
    end
    
    next_max_number = to_reduce -1
    divisor, remainder = total.divmod(next_max_number)
    divisor.times {combination_array << next_max_number}
    if remainder > 0
      combination_array << remainder
    end    
    combination_array = combination_array.sort.reverse
    combinations << Array.new(combination_array)
  end
  max_number -= 1
end

count = 1
combinations.each do |combination|
  if combination.meets_criteria?
    puts "Number #{count} : #{combination.join(', ')}"
    count += 1
  end
end

puts "\n\nTime spent is #{(Time.now - start_time) / 60 } minutes."