[leetcode] A Distance Maximizing Problem的疑问

http://leetcode.com/2011/05/a-distance-maximizing-problem.html

 

问题： Given an array A of integers, find the maximum of j-i subjected to the constraint of A[i] < A[j].

 

解法二：排序后的lookup table是用来做什么的，怎么构造的？

 

解法三：Generally, we want to choose only starting points with no such lines that are shorter to its left side. From the diagram above, only lines of index 0, 1, 3, 4 are valid starting points.  这一步是怎么在O(n)的时间内做到的？