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044-sp_unweighted.py
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044-sp_unweighted.py
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from graph import Graph, State
from collections import deque
class GraphShortestPath(Graph):
def shortest_path(self, source_key, dest_key):
if source_key is None or dest_key is None:
return None
if source_key is dest_key:
return [source_key]
prev_node_keys = self._shortest_path(source_key, dest_key)
if prev_node_keys is None:
return None
else:
path_ids = [dest_key]
prev_node_key = prev_node_keys[dest_key]
while prev_node_key is not None:
path_ids.append(prev_node_key)
prev_node_key = prev_node_keys[prev_node_key]
return path_ids[::-1]
def _shortest_path(self, source_key, dest_key):
queue = deque()
queue.append(self.nodes[source_key])
prev_node_keys = {source_key: None}
self.nodes[source_key].visit_state = State.visited
while queue:
node = queue.popleft()
if node.key is dest_key:
return prev_node_keys
prev_node = node
for adj_node in node.adj_nodes.values():
if adj_node.visit_state == State.unvisited:
queue.append(adj_node)
prev_node_keys[adj_node.key] = prev_node.key
adj_node.visit_state = State.visited
return None