VertexList ordering of a simple graph

Question

Given a simple graph like

g=Graph[{b -> c, a -> b}]

I would like to have f[g] resulting in {a,b,c} but for instance VertexList[g] results {b,c,a} which's not wanted. Is there any simple way to do this?

Answer 1

If you have disordered graph

g = Graph[{b -> c, a -> b}]; VertexList[g]

{b, c, a}

Use sort to find the order

f[g_] := Graph[Sort[VertexList[g]], EdgeList[g]];
VertexList[f[g]]

{a, b, c}

If your graph is directed and acyclic, then you have a built in function to sort based on topological order:

TopologicalSort[g]

{a, b, c}