How can Dijkstra's algorithm apply to both undirected and directed algorithm in one program?

Question

The graph is represented in the format as below:

MAX 12
NODE 1 1
NODE 2 2 
NODE 3 3
NODE 4 4
NODE 5 5
NODE 6 6
NODE 7 7
NODE 9 9
NODE 8 8
NODE 10 10
NODE 11 11
NODE 12 12
EDGE 1 2
EDGE 2 3
EDGE 3 4
EDGE 4 5
EDGE 5 6
EDGE 6 7
EDGE 7 8
EDGE 8 9
EDGE 9 10
EDGE 10 11
EDGE 11 12
EDGE 1 12
EDGE 1 3
EDGE 1 4
EDGE 1 6
EDGE 1 8
EDGE 1 11
EDGE 1 10
EDGE 6 10
EDGE 3 6
EDGE 4 6
EDGE 5 7
EDGE 9 11

I need to use the adjacent list to read in those edges. But if I want to use it as an undirected graph, that is , ignore all the directness of all edges. How could I know the connectivity of each pair of nodes?

For example, the shortest distance between (NODE 2, NODE 8) is 2 (2->1>8) in the undirected graph, but using the Dijkstra's algorithm to this graph gets 4 (2->3->6->7->8). How could I represent the undirected graph while still using the same technique to read in edges?

Answer 1

If you really don't want to change the technique of reading in the edges you'd have to iterate over all the other nodes to see if your node is in their adjacency-list instead of the other way around.

This will increase your running time by quite a bit while not saving you much storage so I'd advise to just change the technique of reading in the edges.