This algorithm is a ruby implementation of the Havel-Hakimi Algorithm.

hakimi.rb

def hakimi n,list
    list = list.sort.reverse
    return true if list.empty? or list[0] == 0
    list.delete(0)
    n = list.shift
    return false if (n > list.length)
    (0..n-1).each {|i| list[i] = (list[i]-1)}
    return hakimi(n, list)
end

list = [5, 3, 0, 2, 6, 2, 0, 7, 2, 5]
puts hakimi(list.length, list)