USACO 2017 February Contest Gold Problem 1

General Questions
#1

Problem Statement: USACO
Problem Anaylsis: Contest Results

I understand most of the solution, but I don’t understand why there are 4 extra elements at the end of both the dr and dc arrays that don’t travel a distance of 3.

#2

bump

#3

Moving EWE is equivalent to moving E.

#4

Thanks, I finally understand that!