| /* |
| * Copyright 2014 Open Networking Laboratory |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| package org.onlab.graph; |
| |
| import java.util.HashSet; |
| import java.util.Set; |
| |
| /** |
| * Implementation of the BFS algorithm. |
| */ |
| public class BreadthFirstSearch<V extends Vertex, E extends Edge<V>> |
| extends AbstractGraphPathSearch<V, E> { |
| |
| @Override |
| public Result<V, E> search(Graph<V, E> graph, V src, V dst, |
| EdgeWeight<V, E> weight, int maxPaths) { |
| checkArguments(graph, src, dst); |
| |
| // Prepare the graph result. |
| DefaultResult result = new DefaultResult(src, dst, maxPaths); |
| |
| // Setup the starting frontier with the source as the sole vertex. |
| Set<V> frontier = new HashSet<>(); |
| result.updateVertex(src, null, 0.0, true); |
| frontier.add(src); |
| |
| boolean reachedEnd = false; |
| while (!reachedEnd && !frontier.isEmpty()) { |
| // Prepare the next frontier. |
| Set<V> next = new HashSet<>(); |
| |
| // Visit all vertexes in the current frontier. |
| for (V vertex : frontier) { |
| double cost = result.cost(vertex); |
| |
| // Visit all egress edges of the current frontier vertex. |
| for (E edge : graph.getEdgesFrom(vertex)) { |
| V nextVertex = edge.dst(); |
| if (!result.hasCost(nextVertex)) { |
| // If this vertex has not been visited yet, update it. |
| double newCost = cost + (weight == null ? 1.0 : weight.weight(edge)); |
| result.updateVertex(nextVertex, edge, newCost, true); |
| // If we have reached our intended destination, bail. |
| if (nextVertex.equals(dst)) { |
| reachedEnd = true; |
| break; |
| } |
| next.add(nextVertex); |
| } |
| |
| if (reachedEnd) { |
| break; |
| } |
| } |
| } |
| |
| // Promote the next frontier. |
| frontier = next; |
| } |
| |
| // Finally, but the paths on the search result and return. |
| result.buildPaths(); |
| return result; |
| } |
| |
| } |