This week's episode will see the return of Lewin Gan, the author of this problem. We'll be discussing the solution to this problem in detail. This problem was the toughest problem in last year's NAIPC. It combines both techniques covered the last two weeks, convex hull optimization and divide and conquer on trees.
Lewin and I used different approaches to solve this problem. You can find both solutions here: http://serjudging.vanb.org/?p=924. We'll be discussing both ideas in detail.
I recommend watching the previous two episodes before this week's episode: