org.apache.drill.common.logical.graph.AdjacencyList.java Source code

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Here is the source code for org.apache.drill.common.logical.graph.AdjacencyList.java

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/*******************************************************************************
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF 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
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package org.apache.drill.common.logical.graph;

import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.Set;

import com.google.common.collect.ArrayListMultimap;
import com.google.common.collect.ListMultimap;
import com.google.common.collect.Multimaps;

public class AdjacencyList<N extends Node<?>> {
    private Set<N> allNodes = new HashSet<N>();
    private ListMultimap<N, Edge<N>> adjacencies = ArrayListMultimap.create();

    public void addEdge(N source, N target, int weight) {
        adjacencies.put(source, new Edge<N>(source, target, weight));
        allNodes.add(source);
        allNodes.add(target);
    }

    public void clearVisited() {
        for (Edge<N> e : adjacencies.values()) {
            e.from.visited = false;
            e.to.visited = false;
        }
    }

    public List<Edge<N>> getAdjacent(N source) {
        return adjacencies.get(source);
    }

    public void printEdges() {
        for (Edge<N> e : adjacencies.values()) {
            System.out.println(e.from.index + " -> " + e.to.index);
        }
    }

    //  public void reverseEdge(Edge<N> e) {
    //    adjacencies.get(e.from).remove(e);
    //    addEdge(e.to, e.from, e.weight);
    //  }

    //  public void reverseGraph() {
    //    adjacencies = getReversedList().adjacencies;
    //  }

    public AdjacencyList<N> getReversedList() {
        AdjacencyList<N> newlist = new AdjacencyList<N>();
        for (Edge<N> e : adjacencies.values()) {
            newlist.addEdge(e.to, e.from, e.weight);
        }
        return newlist;
    }

    public Set<N> getNodeSet() {
        return adjacencies.keySet();
    }

    /**
     * Get a list of nodes that have no outbound edges.
     * @return
     */
    public Collection<N> getTerminalNodes() {
        // we have to use the allNodes list as otherwise destination only nodes won't be found.
        List<N> nodes = new LinkedList<N>(allNodes);

        for (Iterator<N> i = nodes.iterator(); i.hasNext();) {
            final N n = i.next();

            // remove any nodes that have one or more outbound edges.
            List<Edge<N>> adjList = this.getAdjacent(n);
            if (adjList != null && !adjList.isEmpty())
                i.remove();

        }
        return nodes;
    }

    /**
     * Get a list of all nodes that have no incoming edges.
     * @return
     */
    public Collection<N> getStartNodes() {
        Set<N> nodes = new HashSet<N>(getNodeSet());
        for (Edge<N> e : adjacencies.values()) {
            nodes.remove(e.to);
        }
        return nodes;
    }

    public Collection<Edge<N>> getAllEdges() {
        return adjacencies.values();
    }

    public void fix() {
        adjacencies = Multimaps.unmodifiableListMultimap(adjacencies);
        allNodes = Collections.unmodifiableSet(allNodes);
    }
}