Hi !

Let Gr=(V,A) a complete symmetric directed a*b grid graph. Arcs are unweighted.

a and b are respectively the width and the height of Gr. I suppose that a>=b. |V| = a*b

I want to count the number of vertices pairwise which are at distance equal to L in the grid. L is at least equal to 1 and at most equal to a+b.

Any ideas ?