number_solitare.rb

def solution(a)
    sum = a[0]
    sum += a[-1] if a[-1] < 0
    negative = []
    a[1..-1].each_with_index do |el,i|
        if el >= 0
            sum+=el
        elsif i==a.size-2 || a[i+2]>=0
            chunk = (i+1).downto(1).take_while{|j| a[j]<0}
            negative << a[chunk.last..chunk.first] if chunk.size>=6
        end
    end

    negative.each do |chunk|
      sum+=chunk.each_slice(6).inject{|s,m| 6.times{|j| s[j]= s.max+m[j].to_i}; s}.max
    end

    sum
end