Problem #67

67.rb

tri = File.open('triangle.txt').map do |row|
	row.split.map {|i| i.to_i}
end

tri.to_enum.with_index do |row, ri|
	row.to_enum.with_index do |n, ni|
		pl = (ri == 0 || ni == 0) ? 0 : tri[ri-1][ni-1]
		pr = (ri == 0 || (ni + 1) == row.length) ? 0 : tri[ri-1][ni]
		p_max = [pl, pr].max
		row[ni] = row[ni] + p_max
	end
end

puts tri.last.max