gh-37662: Add parameter `sort_neighbors` to method `init_short_digraph`
Fixes #37642.
We add parameter `sort_edges` to method `init_short_digraph` of the
`short_digraph` data structure defined in
`src/sage/graphs/base/static_sparse_graph.pxd|pyx`.
- When set to `True` (default), for each vertex, the list of neighbors
is sorted by increasing vertex labels. This enables to search for a
vertex in this list using binary search, and so in time `O(log(n))`, but
the overall running time of method `init_short_digraph` is in `O(m +
n*log(m))`.
- When set to `False`, neighbors are not sorted. The running time of
method `init_short_digraph` is reduced to `O(n + m)`, but the running
time for searching in the list of neighbors increases to `O(m)`.
So this new parameter is particularly useful for linear time algorithms
such as `lex_BFS`.
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### :hourglass: Dependencies
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URL: https://github.com/sagemath/sage/pull/37662
Reported by: David Coudert
Reviewer(s):
