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Fix reporting weight in yen_k_shortest_simple_paths #40248

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Merged
merged 3 commits into from
Jun 25, 2025
Merged

Fix reporting weight in yen_k_shortest_simple_paths #40248

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e8362fd
report weight if s=t in yen_k_shortest_simple_paths
kappybar Jun 12, 2025
f2ef353
change to shorter code
kappybar Jun 12, 2025
77a304f
Merge branch 'develop' into report_weight_in_yen
kappybar Jun 15, 2025
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14 changes: 8 additions & 6 deletions src/sage/graphs/path_enumeration.pyx
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Original file line number Diff line number Diff line change
Expand Up @@ -734,19 +734,21 @@ def yen_k_shortest_simple_paths(self, source, target, weight_function=None,
[1, 6, 9, 10, 5],
[1, 6, 9, 3, 4, 5],
[1, 6, 9, 11, 10, 5]]

When ``s == t`` and ``report_edge == True`` and ``report_weight == True`` (:issue:`40247`)::

sage: g = DiGraph([(1, 2)])
sage: list(yen_k_shortest_simple_paths(g, 1, 1, report_edges=True, report_weight=True))
[(0, [])]
"""
if source not in self:
raise ValueError("vertex '{}' is not in the graph".format(source))
if target not in self:
raise ValueError("vertex '{}' is not in the graph".format(target))

if source == target:
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A shorter version could be

if source == target:
    P = [] if report_edges else [source]
    yield (0, P) if report_weight else P

if report_edges:
yield []
elif report_weight:
yield (0, [source])
else:
yield [source]
P = [] if report_edges else [source]
yield (0, P) if report_weight else P
return

if self.has_loops() or self.allows_multiple_edges():
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