1def assert(x, y)
 2  raise [x, y].inspect unless x == y
 3end
 4
 5class Solution
 6  def self.run(buildings)
 7    changes = []
 8    result = []
 9    buildings.each do |building|
10      left, right, height = building
11      left.upto(right) do |n|
12        changes[n] = height
13      end
14    end
15    current = nil
16    changes.each_with_index do |item, index|
17      next if item == current
18
19      current = item
20      result << [index, item]
21    end
22    result << [changes.size, 0]
23    result
24  end
25end
26
27assert Solution.run([[2,8,3], [4,6,5]]), [[2,3], [4,5], [7,3], [9,0]]