1 files changed, 181 insertions, 0 deletions
diff --git a/com/example/portfolio3/Graphs.java b/com/example/portfolio3/Graphs.java
new file mode 100644
index 0000000..54cad9e
--- /dev/null
+++ b/com/example/portfolio3/Graphs.java
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+import java.util.*;
+public class Graphs {}
+
+class Vertex{
+  private String name;
+  public String name(){return name;}
+  public Vertex(String s){name=s;}
+  public String toString(){return name;}
+}
+class Edge{
+  private Vertex from,to;
+  private int weight;
+  public Vertex from(){return from;}
+  public Vertex to(){return to;}
+  public int weight(){return weight;}
+  Edge(Vertex from,Vertex to,int w){this.from=from; this.to=to; weight=w;}
+  public String toString(){return from.name()+" - "+weight+" -> "+to.name(); }
+}
+interface Graph {
+  void insertEdge(String v, String u, int w);
+  Collection<Vertex> vertices();
+  Collection<Edge> edges();
+  Collection<Edge> outEdge(Vertex v);
+  Integer getWeight(Vertex v1, Vertex v2);
+}
+
+abstract class AbstractGraph implements Graph{
+  private HashMap<String,Vertex> vertexMap=new HashMap<>();
+  private HashSet<Vertex> vertexSet=new HashSet<>();
+  public Vertex vertex(String s){
+    if(vertexMap.containsKey(s))return vertexMap.get(s);
+    Vertex v=new Vertex(s);
+    vertexMap.put(s,v);
+    vertexSet.add(v);
+    return v;
+  }
+  public void insertEdge(String v, String u, int w){
+    insertEdge(vertex(v),vertex(u),w);
+  }
+  public Collection<Vertex> vertices() { return vertexSet;  }
+  //
+  abstract public void insertEdge(Vertex v1, Vertex v2, int w);
+  abstract public Collection<Edge> edges();
+  abstract public Collection<Edge> outEdge(Vertex v);
+  abstract public Integer getWeight(Vertex v1, Vertex v2);
+}
+
+//--------------------------------------------------------
+//  EdgeGraph - One big set of all edges in the graph
+
+class EdgeGraph extends AbstractGraph {
+  Set<Edge> edges=new HashSet<>();
+  public void insertEdge(Vertex v1,Vertex v2,int w){
+    edges.add(new Edge(v1,v2,w));
+  }
+  public Collection<Edge> edges(){return edges;}
+  public Collection<Edge> outEdge(Vertex v){
+    ArrayList<Edge> outEdge=new ArrayList<>();
+    for(Edge e:edges)if(e.from()==v)outEdge.add(e);
+    return outEdge;
+  }
+  public Integer getWeight(Vertex v1,Vertex v2){
+    // linear in number of edges in the graph
+    for(Edge e:edges){
+      if(e.from()==v1 && e.to()==v2)return e.weight();
+    }
+    return null;
+  }
+}
+
+//--------------------------------------------------------
+//  Adjecency List Graph - A map from vertices to set of outedges from the vertex
+
+class AdjListGraph extends AbstractGraph {
+  private Map<Vertex,Set<Edge>> outEdge= new HashMap<>();
+  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 HashSet<Edge>());
+    outEdge.get(e.from()).add(e);
+  }
+  public Collection<Edge> edges(){
+    Set<Edge> edges=new HashSet<>();
+    for(Vertex v:outEdge.keySet())edges.addAll(outEdge.get(v));
+    return edges;
+  }
+  public Collection<Edge> outEdge(Vertex v){
+    if(!outEdge.containsKey(v))
+      return new HashSet<Edge>();
+    return outEdge.get(v);
+  }
+  public Integer getWeight(Vertex v1,Vertex v2){
+    // linear in number of outedges from vertices
+    if(!outEdge.containsKey(v1))return null;
+    for(Edge e:outEdge.get(v1)){
+      if(e.to()==v2)return e.weight();
+    }
+    return null;
+  }
+}
+
+//--------------------------------------------------------
+//  Adjecency Map Graph - A map from vertices to map of target vertex to edge
+
+class AdjMapGraph extends AbstractGraph {
+  private Map<Vertex, Map<Vertex, Edge>> outEdge = new HashMap<>();
+
+  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);
+  }
+  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;
+  }
+  public Collection<Edge> outEdge(Vertex v) {
+    return outEdge.get(v).values();
+  }
+  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();
+  }
+}
+
+//--------------------------------------------------------
+//  Matrix Graph:  weights are stored in a twodimensional array
+
+class MatrixGraph extends AbstractGraph {
+  private Integer[][] matrix=null; // made in constructor
+  // We must be able to map vertices to index in matrix and back again
+  private Vertex[] index2vertex; // made in constructor
+  private Map<Vertex,Integer> vertex2index=new HashMap<>();
+  private int numVertex; // maximum number of vertices
+  MatrixGraph(int numVertex){ // maximum number of vertices allowed
+    this.numVertex=numVertex;
+    matrix =new Integer[numVertex][numVertex];
+    index2vertex=new Vertex[numVertex];
+  }
+  private int getIndex(Vertex v){
+    if(vertex2index.containsKey(v)) return vertex2index.get(v);
+    int index=vertex2index.size();
+    if(index>=index2vertex.length)throw new RuntimeException("Too many vertices in graph");
+    vertex2index.put(v,index);
+    index2vertex[index]=v;
+    return index;
+  }
+  public void insertEdge(Vertex v1,Vertex v2,int w){
+    matrix[getIndex(v1)][getIndex(v2)] = w;
+  }
+  public Collection<Edge> edges(){
+    HashSet<Edge> edges=new HashSet<>();
+    for(int i=0;i<numVertex;i++){
+      for(int j=0;j<numVertex;j++){
+        Integer weight=matrix[i][j]; // may be null
+        if(weight==null)continue;
+        edges.add(new Edge(index2vertex[i],index2vertex[j],weight));
+      }
+    }
+    return edges;
+  }
+  public Collection<Edge> outEdge(Vertex v1){
+    HashSet<Edge> edges=new HashSet<>();
+    int i=vertex2index.get(v1);
+    for(int j=0;j<numVertex;j++){
+      Integer weight=matrix[i][j]; // may be null
+      if(weight==null)continue;
+      edges.add(new Edge(v1,index2vertex[j],weight));
+    }
+    return edges;
+  }
+  public Integer getWeight(Vertex v1,Vertex v2){
+    // constant time operation
+    return matrix[vertex2index.get(v1)][vertex2index.get(v2)];}
+}