def volume(left_edge, right_edge, length, dirt)
  cap = [left_edge, right_edge].min
  [(cap*length-dirt),0].max
end

def water_helper(left_edge, index, count, dirt, right_edge, blocks)
  puts("#{left_edge}, #{index}, #{count}, #{dirt}, #{right_edge}") if $debug
  if index == blocks.size-1
    water_volume = volume(left_edge, right_edge, count, dirt)
    puts("end: water_volume") if $debug
    water_volume
  elsif blocks[index] > right_edge
    water_volume = volume(left_edge, blocks[index], count, dirt)
    puts("split: water_volume") if $debug
    water_volume + water_helper(blocks[index], index+1, 0, 0, right_edge, blocks)
  else
    water_helper(left_edge, index+1, count+1,blocks[index]+dirt, right_edge, blocks)
  end
end

def waterblocks(blocks)
  return 0 if blocks.size <= 2
  water_helper(blocks.first,1,0,0, blocks.last, blocks)
end

testcases = [
  [[5, 5], 0],
  [[5, 1, 10], 4],
  [[10, 1, 5], 4],
  [[10, 1, 5, 5], 4],
  [[10, 5, 1, 5], 4],
  [[10, 1, 1, 5], 8],
  [[10, 5, 1], 0],
  [[1, 5, 10], 0],
  [[5, 2, 3, 2, 1, 3], 4],
  [[5, 4, 6,1,6,4,5], 7],
  [[1,1,3,1,5,1,1],2],
]

testcases.each do |info|
  data = info.first
  expected = info.last
  actual = waterblocks(data)
  if expected == actual
    puts "Passed: #{data}"
  else
    $debug = true
    waterblocks(data)
    puts "Failed: #{data}"
    puts "Actual: #{actual} Expected: #{expected}"
    $debug = false
  end
end