py3: avoid sorting vertices and edges in method treewidth

[dcoudert]

We avoid sorting vertices, edges and connected components. The code is better this way, and this fixes a doctest error with py3.

CC: @tscrim @fchapoton

Component: graph theory

Author: David Coudert

Branch/Commit: f830eb9

Reviewer: Travis Scrimshaw

Issue created by migration from https://trac.sagemath.org/ticket/27009

[dcoudert]

Commit: f830eb9

[dcoudert]

New commits:

f830eb9

trac #27009: avoid sorting in method treewidth

[dcoudert]

Branch: public/27009_treewidth

[tscrim]

comment:2

Why do you use for v in G.vertices(sort=False): instead of one of the iterators?

Other than that LGTM.

[dcoudert]

comment:3

The graph is modified inside the loop over all vertices, so I cannot use an iterator here (at least it's safer this way).
So we can use either G.vertices(sort=False) or list(G).

[tscrim]

comment:4

Okay, thanks for the explanation. LGTM.

[tscrim]

Reviewer: Travis Scrimshaw

[dcoudert]

comment:5

Thank you for the reviews and happy new year !

[embray]

comment:6

Retarging tickets optimistically to the next milestone. If you are responsible for this ticket (either its reporter or owner) and don't believe you are likely to complete this ticket before the next release (8.7) please retarget this ticket's milestone to sage-pending or sage-wishlist.

[vbraun]

Changed branch from public/27009_treewidth to f830eb9