View source for DAG Longest Path

Each node gets the length of the longest directed path from any source in the directed acyclic graph (DAG).
A source in DAG is a node which has only outgoing links.

If the graph has cycles, each strongly connected component is aggregated to one node which results in a DAG.
In this case, each vertex gets the longest directed path from any strongly connected component whose nodes do not have any incoming edge to a node of another strongly connected component.