helper.preorder_st_traversal

helper.preorder_st_traversal(H, T)

Conducts a pre-ordered traversal of tree T with an s-t orientation.

s is the source node and t is the target node for the PDP. Traversal of an s-t oriented tree involves traversing the tree in pre-order, but leaving the branch with t to be visited last at each step possible.

Parameters:

• H (graph) – The request graph.
• T (graph) – A spanning tree of H.

Returns:

P – PDP tour solution.

Return type:

graph