I use sqrt decomposition and some DP.
My DP idea is to keep for each robot the shortest path which we can find if we detour by left or right. And I use sqrt decomposition to find the next encountered robot on the current path.
Could someone give me a tricky example?

Edit: I wrote the update of the sqrt decomposition again(different) and now I get WA23.

Edited by author 22.09.2010 15:13