src/com.example.portfolio3/com/example/portfolio3/AdjMapGraph.java



package com.example.portfolio3;

// origin: <https://moodle.ruc.dk/course/section.php?id=211877>

import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;

/// Adjecency Map Graph - A map from vertices to map of target vertex to edge
class AdjMapGraph extends AbstractGraph {

    /// foo
    AdjMapGraph() { }

    /// foo
    private Map<Vertex, Map<Vertex, Edge>> outEdge = new HashMap<>();

    /// foo
    public void insertEdge(final Vertex v1, final Vertex v2, final int w) {
        Edge e = new Edge(v1, v2, w);
        if (!outEdge.containsKey(e.from())) {
            outEdge.put(e.from(), new HashMap<Vertex, Edge>());
        }
        outEdge.get(e.from()).put(e.to(), e);
    }

    /// foo
    public Collection<Edge> edges() {
        Set<Edge> edges = new HashSet<>();
        for (Vertex v : outEdge.keySet()) {
            for (Vertex w : outEdge.get(v).keySet()) {
                edges.add(outEdge.get(v).get(w));
            }
        }

        return edges;
    }

    /// foo
    public Collection<Edge> outEdge(final Vertex v) {
        return outEdge.get(v).values();
    }

    /// foo
    public Integer getWeight(final Vertex v1, final Vertex v2) {
        // constant time operation
        if (!outEdge.containsKey(v1)) {
            return null;
        }
        if (!outEdge.get(v1).containsKey(v2)) {
            return null;
        }

        return outEdge.get(v1).get(v2).weight();
    }
}