ruby solutions for http://qandwhat.apps.runkite.com/i-failed-a-twitter-interview/ and https://gist.github.com/mkozakov/59af0fd5bddbed1a0399

twitter-solutions-1.rb

{
  original: -> land {
    left_max = 0
    right_max = 0
    left = 0
    right = land.length - 1
    volume = 0

    while left < right
      if land[left] > left_max
        left_max = land[left]
      end

      if land[right] > right_max
        right_max = land[right]
      end

      if left_max >= right_max
        volume += right_max - land[right]
        right -= 1
      else
        volume += left_max - land[left]
        left += 1
      end
    end

    volume
  },

  easy: -> land {
    v = 0
    land.each_with_index do |h, i|
      v += [[land[0..i].max, land[i..-1].max].min - h, 0].max
    end
    v
  }
}.each do |name, func|
  print name.to_s
  {
    [1,2,3,4,5,4,5,3] => 1,
    [2,1,2,3,4,2] => 1,
    [5,1,5] => 4,
    [2,7,2,7,4,7,1,7,3,7] => 5+3+6+4,
    [5,1,0,1] => 1,
    [2,5,1,2,3,4,7,7,6,3,5] => 12
  }.each do |land, volume|
    print func.call(land) == volume ? '.' : 'F'
  end
  print "\n"
end