leetcode -- The Skyline Problem -- 难理解，关于heap

https://leetcode.com/problems/the-skyline-problem/

基本没理解，再看看

思路1 divide and conquer

http://www.geeksforgeeks.org/divide-and-conquer-set-7-the-skyline-problem/
code参考
http://blog.youkuaiyun.com/pointbreak1/article/details/46369559

思路2 heap

http://bookshadow.com/weblog/2015/08/14/leetcode-the-skyline-problem/
https://segmentfault.com/a/1190000003786782