MIT 6006 Quiz 2: The shortest path task I'm looking for some clarifications on an algorithmic task I've been trying to solve. This task is a part of Quiz 2 from the MIT 6.006 course.
The main idea of creating k-copies of a graph G is clear. What I'm really confused with is the final graph G':

Can you explain how the graph G' will look like?
How will the G' graph guarantee that all of the places {v0, v1, v2, vi} had been visited once we reached the destination vertex t?

I'm sorry if the community to post this question is wrong. Any suggestions are highly appreciated.
Input:

Solution:
Ok, I think here is how it should look like. You duplicate the graph G as many times as many v places you have to visit (e.g. v0, v1, v2). The order you must visit these vertices is the constraint which is expressed as zero weight edges (G1.v0 -&gt; G2.v0, G2.v1 -&gt; G3.v1).