Example usage for com.google.common.graph ValueGraphBuilder build

Introduction

In this page you can find the example usage for com.google.common.graph ValueGraphBuilder build.

Prototype

public <N1 extends N, V1 extends V> MutableValueGraph<N1, V1> build() 

Source Link

Document

Returns an empty MutableValueGraph with the properties of this ValueGraphBuilder .

Usage

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.// w  w w .java  2  s.c  o m
 *
 * @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;
}

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