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(Vertex v1, Vertex v2, 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(Vertex v) {
    return outEdge.get(v).values();
  }

  /// foo
  public Integer getWeight(Vertex v1, 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();
  }
}