def dfs_edges(node, type_):
'''
Iterative DFS, based on http://www.ics.uci.edu/~eppstein/PADS/DFS.py
Returns forward and reverse edges. Also returns root node in correct
order for pre- (FORWARD) and post- (BACKWARD) ordering.
``type_`` selects which values are iterated over. Children which are
not of this type are flagged with LEAF.
'''
while isinstance(node, type_):
try:
stack = [(node, iter(node), ROOT)]
yield node, node, FORWARD | ROOT
visited = set()
visited = fallback_add(visited, node)
while stack:
parent, children, p_type = stack[-1]
try:
child = next(children)
if isinstance(child, type_):
if safe_in(child, visited, False):
yield parent, child, NON_TREE
else:
stack.append((child, iter(child), NODE))
yield parent, child, FORWARD | NODE
visited = fallback_add(visited, child)
else:
stack.append((child, empty(), LEAF))
yield parent, child, FORWARD | LEAF
except StopIteration:
stack.pop()
if stack:
yield stack[-1][0], parent, BACKWARD | p_type
yield node, node, BACKWARD | ROOT
return
except Reset:
yield # in response to the throw (ignored by caller)
def dfs_edges(node, type_):
'''
Iterative DFS, based on http://www.ics.uci.edu/~eppstein/PADS/DFS.py
Returns forward and reverse edges. Also returns root node in correct
order for pre- (FORWARD) and post- (BACKWARD) ordering.
``type_`` selects which values are iterated over. Children which are
not of this type are flagged with LEAF.
'''
while isinstance(node, type_):
try:
stack = [(node, iter(node), ROOT)]
yield node, node, FORWARD | ROOT
visited = set()
visited = fallback_add(visited, node)
while stack:
parent, children, p_type = stack[-1]
try:
child = next(children)
if isinstance(child, type_):
if safe_in(child, visited, False):
yield parent, child, NON_TREE
else:
stack.append((child, iter(child), NODE))
yield parent, child, FORWARD | NODE
visited = fallback_add(visited, child)
else:
stack.append((child, empty(), LEAF))
yield parent, child, FORWARD | LEAF
except StopIteration:
stack.pop()
if stack:
yield stack[-1][0], parent, BACKWARD | p_type
yield node, node, BACKWARD | ROOT
return
except Reset:
yield # in response to the throw (ignored by caller)
def loops(node, type_):
'''
Return all loops from the given node.
Each loop is a list that starts and ends with the given node.
'''
stack = [[node]]
known = {node} # avoid getting lost in sub-loops
while stack:
ancestors = stack.pop()
parent = ancestors[-1]
if isinstance(parent, type_):
for child in parent:
family = list(ancestors)
family.append(child)
if child is node:
yield family
else:
if not safe_in(child, known):
stack.append(family)
known = fallback_add(known, child)
def loops(node, type_):
'''
Return all loops from the given node.
Each loop is a list that starts and ends with the given node.
'''
stack = [[node]]
known = {node} # avoid getting lost in sub-loops
while stack:
ancestors = stack.pop()
parent = ancestors[-1]
if isinstance(parent, type_):
for child in parent:
family = list(ancestors)
family.append(child)
if child is node:
yield family
else:
if not safe_in(child, known):
stack.append(family)
known = fallback_add(known, child)