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−# Copyright (c) 2007-2008 Pedro Matiello <pmatiello@gmail.com>
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−#
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−# Permission is hereby granted, free of charge, to any person
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−# obtaining a copy of this software and associated documentation
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−# files (the "Software"), to deal in the Software without
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−# restriction, including without limitation the rights to use,
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−# copy, modify, merge, publish, distribute, sublicense, and/or sell
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−# copies of the Software, and to permit persons to whom the
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−# Software is furnished to do so, subject to the following
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−# conditions:
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−
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−# The above copyright notice and this permission notice shall be
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−# included in all copies or substantial portions of the Software.
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−
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−# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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−# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
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−# OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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−# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
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−# HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
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−# WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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−# FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
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−# OTHER DEALINGS IN THE SOFTWARE.
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−
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−
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−"""
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−Traversal algorithms for python-graph.
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−
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−@sort: traversal
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−"""
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−
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−
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−# Minimal spanning tree
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−
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−def traversal(graph, node, order):
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−	"""
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−	Graph traversal iterator.
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−
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−	@type  node: node
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−	@param node: Node.
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−	
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−	@type  order: string
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−	@param order: traversal ordering. Possible values are:
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−		2. 'pre' - Preordering (default)
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−		1. 'post' - Postordering
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−	
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−	@rtype:  iterator
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−	@return: Traversal iterator.
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−	"""
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−	visited = {}
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−	if (order == 'pre'):
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−		pre = 1
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−		post = 0
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−	elif (order == 'post'):
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−		pre = 0
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−		post = 1
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−	
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−	for each in _dfs(graph, visited, node, pre, post):
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−		yield each
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−
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−
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−def _dfs(graph, visited, node, pre, post):
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−	"""
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−	Depht-first search subfunction for traversals.
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−	
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−	@type  graph: graph
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−	@param graph: Graph.
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−
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−	@type  visited: dictionary
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−	@param visited: List of nodes (visited nodes are marked non-zero).
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−
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−	@type  node: node
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−	@param node: Node to be explored by DFS.
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−	"""
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−	visited[node] = 1
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−	if (pre): yield node
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−	# Explore recursively the connected component
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−	for each in graph[node]:
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−		if (each not in visited):
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−			for other in _dfs(graph, visited, each, pre, post):
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−				yield other
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−	if (post): yield node