I am working on Problem 1 from the CROATIAN HIGH SCHOOL COMPETITIONS IN INFORMATICS 2014 Final Exam #2.

Problem

Solution

I don't understand the part of the solution about transforming the original edges into nodes. How do we find the shortest path after the transformation? What is stored in each node of the new graph? An explanation with example would be appreciated.

I am confused on the second solution with min-cost flow. Specifically, what do they mean in the second paragraph which starts "Unfortunately, the permutation of cows ..."?

Problem: http://usaco.org/index.php?page=viewproblem2&cpid=248 Solution http://usaco.org/current/data/sol_taxi.html