You are competing in a ski slalom, and you need to select the best skis for the race. The format of the race is that there are
Npairs of left and right gates, where each right gate is
Wmetres to the right of its corresponding left gate, and you may neither pass to the left of the left gate nor to the right of the right gate. The
ithpair of gates occurs at distance
yidown the hill, with the horizontal position of the
ithleft gate given by
xi. Each gate is further down the hill than the previous gate (i.e.
yi<
yi+1for all
i).
You may select from S pairs of skis, where the jth pair has speed sj. Your movement is governed by the following rule: if you select a pair of skis with speed sj, you move with a constant downward velocity of sj metres per second. Additionally, at any time you may move at a horizontal speed of at most vh metres per second.
You may start and finish at any two horizontal positions. Determine which pair of skis will allow you to get through the race course, passing through all the gates, in the shortest amount of time.