for P piles with N items, generate all possible combinations without redundant

gen-piles.rb

# for P piles with N items, generate all possible combinations without redundant
# e.g. for piles(5, 3) -> [(5,0,0), (4,1,0), (3,2,0), (3,1,1), (2,2,1)] 
def make_piles (num, pile, piles=[], c=Array.new(pile, 0), idx=0)
  if num == 0
    piles.push(c.clone)
  else
    top = (c[idx-1] != 0) ? ((c[idx-1] > num) ? num : c[idx-1]) : (num)
    top.downto(1).each do |i|
      c[idx] = i
      make_piles(num-i, pile, piles, c, idx+1)
      c[idx] = 0
    end
  end
 
  return piles
end
 
piles = make_piles(50, 50)
puts piles.map{|p| p.inspect}.join("\n")