https://paiza.jp/poh/enkoi #3

enkoi-3.rb

# 自分の得意な言語で
# Let's チャレンジ！！
 
# Rubyは怖いです

# too slow QQ
=begin
block, total = gets.split(" ").map{|i| i.to_i}

pieces = total.times.map{gets.to_i}

puts (0..total-block).map { |i|
        pieces[i, block].inject(&:+)
    }.max
=end

# ... It's not so pretty T_T
block, total = gets.split(" ").map{|i| i.to_i}
pieces = total.times.map{gets.to_i}

# block calcing now = max value found = total of first block (?)
block_total = max_now = pieces[0, block].inject(&:+)

(block...total).each do |i|
  block_total = block_total - pieces[i - block] + pieces[i]
  max_now = block_total if block_total > max_now
end

puts max_now