Example usage for com.google.common.graph MutableValueGraph addNode

Introduction

In this page you can find the example usage for com.google.common.graph MutableValueGraph addNode.

Prototype

@CanIgnoreReturnValue
boolean addNode(N node);

Source Link

Document

Adds node if it is not already present.

Usage

From source file:io.acoia.graphs.MinimumSpanningTree.java

/**
 * An implementation of Kruskal's minimum spanning tree algorithm.
 * // www .j a v  a  2s.  c o  m
 * Description from Wiki: Kruskal's algorithm is a minimum-spanning-tree algorithm which finds an
 * edge of the least possible weight that connects any two trees in the forest. It is a greedy
 * algorithm in graph theory as it finds a minimum spanning tree for a connected weighted graph
 * adding increasing cost arcs at each step. This means it finds a subset of the edges that forms
 * a tree that includes every vertex, where the total weight of all the edges in the tree is
 * minimized. If the graph is not connected, then it finds a minimum spanning forest (a minimum
 * spanning tree for each connected component).
 * 
 * This implementation uses io.acoia.sets.UnionFind and expects a sorted list of edges, and thus
 * runs in O(E (V)) time.
 */
public static <E, N> ValueGraph<N, E> kruskals(ValueGraph<N, E> g, List<EndpointPair<N>> sortedEdges) {

    if (g.isDirected())
        throw new IllegalArgumentException("Kruskal's does not support directed graphs");

    // Set up a Graph to store the result. 
    MutableValueGraph<N, E> tree = ValueGraphBuilder.undirected().allowsSelfLoops(false)
            .expectedNodeCount(g.nodes().size()).build();

    for (N n : g.nodes()) {
        tree.addNode(n);
    }

    // Now we start kruskals.. most of the work is done by the UnionFind really...
    UnionFind<N> uf = new UnionFind<>(g.nodes());
    for (EndpointPair<N> e : sortedEdges) {

        N nodeU = e.nodeU();
        N nodeV = e.nodeV();

        if (uf.findRoot(nodeU) != uf.findRoot(nodeV)) {
            tree.putEdgeValue(nodeU, nodeV, g.edgeValue(nodeU, nodeV));
            uf.join(nodeU, nodeV);
        }
    }

    return tree;
}

---

From source file:edu.uci.ics.jung.algorithms.transformation.NodePartitionCollapser.java

/**
 * Creates a new graph whose nodes correspond to the partitions of the supplied graph. Two nodes u
 * and v in the collapsed graph will be connected if there is an edge between any of the nodes in
 * u and any of the nodes in v, and u and v are distinct. The value of the edge represents the
 * number of such edges.//from   ww  w .  ja  va  2s  .  c om
 *
 * @param partitioning a node partition of a graph
 * @return the collapsed graph
 */
public static <N> ValueGraph<Set<N>, Integer> collapseNodePartitions(NodePartition<N> partitioning) {
    Graph<N> original = partitioning.getGraph();
    ValueGraphBuilder<Object, Object> builder = original.isDirected() ? ValueGraphBuilder.directed()
            : ValueGraphBuilder.undirected();
    MutableValueGraph<Set<N>, Integer> collapsed = builder.build();

    // create nodes in new graph corresponding to equivalence sets in the original graph
    for (Set<N> set : partitioning.getNodePartitions()) {
        collapsed.addNode(set);
    }

    // for each pair of endpoints in the original graph, connect the corresponding nodes
    // (representing partitions) in the collapsed graph if the partitions are different
    Map<N, Set<N>> nodeToPartition = partitioning.getNodeToPartitionMap();
    for (EndpointPair<N> endpoints : original.edges()) {
        N nodeU = endpoints.nodeU();
        N nodeV = endpoints.nodeV();
        Set<N> partitionU = nodeToPartition.get(nodeU);
        Set<N> partitionV = nodeToPartition.get(nodeV);
        if (nodeU.equals(nodeV) || partitionU.equals(partitionV)) {
            // we only connect partitions if the partitions are different;
            // check the nodes first as an optimization
            continue;
        }

        int edgeCount = collapsed.edgeValueOrDefault(partitionU, partitionV, 0);
        collapsed.putEdgeValue(partitionU, partitionV, edgeCount + 1);
    }
    return collapsed;
}

---

From source file:org.jgrapht.graph.guava.ImmutableValueGraphAdapter.java

@SuppressWarnings("unchecked")
private void readObject(ObjectInputStream ois) throws ClassNotFoundException, IOException {
    ois.defaultReadObject();//from   w  w w .  ja  va 2  s.  c  o m

    GraphType type = (GraphType) ois.readObject();
    if (type.isMixed() || type.isAllowingMultipleEdges()) {
        throw new IOException("Graph type not supported");
    }

    MutableValueGraph<V, W> mutableValueGraph = (type.isDirected() ? ValueGraphBuilder.directed()
            : ValueGraphBuilder.undirected()).allowsSelfLoops(type.isAllowingSelfLoops()).build();

    // read vertices
    int n = ois.readInt();
    for (int i = 0; i < n; i++) {
        V v = (V) ois.readObject();
        mutableValueGraph.addNode(v);
    }

    // read edges
    int m = ois.readInt();
    for (int i = 0; i < m; i++) {
        V s = (V) ois.readObject();
        V t = (V) ois.readObject();
        W w = (W) ois.readObject();
        mutableValueGraph.putEdgeValue(s, t, w);
    }

    // setup the immutable copy
    this.valueGraph = ImmutableValueGraph.copyOf(mutableValueGraph);
}

---