# Copyright (c) 2007-2008 Pedro Matiello <pmatiello@gmail.com>
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"""
Sorting algorithms for python-graph.

@sort: topological_sorting
"""


# Topological sorting

def topological_sorting(graph):
	"""
	Topological sorting.

	@attention: Topological sorting is meaningful only for directed acyclic graphs.

	@type  graph: graph
	@param graph: Graph.

	@rtype:  list
	@return: Topological sorting for the graph.
	"""
	# The topological sorting of a DAG is equivalent to its reverse postordering.
	tmp, tmp, post = graph.depth_first_search()
	post.reverse()
	return post