You are given a graph and an algorithm that can find the shortest path b/w any two nodes.
Now you have to find the second shortest path between same two nodes.
From the top answer:
Find the shortest path between any two nodes. Let them be A and B.
Now to get second shortest path between the same nodes, remove any one edge that is involved in the shortest path between the same nodes and calculate the shortest path.
Do the above process for each of the node involved in shortest path and keep track of the minimum second shortest path found.