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GraphHopper is a fast and memory efficient Java road routing engine working seamlessly with OpenStreetMap data.

There is a newer version: 10.0

/*
 *  Licensed to GraphHopper GmbH under one or more contributor
 *  license agreements. See the NOTICE file distributed with this work for
 *  additional information regarding copyright ownership.
 *
 *  GraphHopper GmbH licenses this file to you 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 com.graphhopper.util;

import com.carrotsearch.hppc.IntArrayDeque;
import com.graphhopper.coll.GHBitSet;

/**
 * Implementation of depth first search (DFS) by LIFO queue
 *
 * @author Peter Karich
 * @author Jan Sölter
 */
public abstract class DepthFirstSearch extends XFirstSearch {
    /**
     * beginning with startNode add all following nodes to LIFO queue. If node has been already
     * explored before, skip reexploration.
     */
    @Override
    public void start(EdgeExplorer explorer, int startNode) {
        IntArrayDeque stack = new IntArrayDeque();

        GHBitSet explored = createBitSet();
        stack.addLast(startNode);
        int current;
        while (stack.size() > 0) {
            current = stack.removeLast();
            if (!explored.contains(current) && goFurther(current)) {
                EdgeIterator iter = explorer.setBaseNode(current);
                while (iter.next()) {
                    int connectedId = iter.getAdjNode();
                    if (checkAdjacent(iter)) {
                        stack.addLast(connectedId);
                    }
                }
                explored.add(current);
            }
        }
    }

}