In this section we consider the all-pairs, shortest path problem:
Given an edge-weighted graph ,
for each pair of vertices in
find the length of the shortest weighted path between the two vertices.
One way to solve this problem is to run Dijkstra's algorithm times
in turn using each vertex in
as the initial vertex.
Therefore, we can solve the all-pairs problem in
time when adjacency lists are used, and
,
when adjacency matrices are used.
However, for a dense graph (
) the running time
of Dijkstra's algorithm is
,
regardless of the representation scheme used.