data_structures_free

net/datastructures/FindPathDFS.java

@@ -0,0 +1,38 @@
+package net.datastructures;
+
+//begin#fragment FindPathDFS
+/** Class specializing DFS to find a path between a start vertex and a target 
+  * vertex. It assumes the target vertex is passed as the info object to the 
+  * execute method. It returns an iterable list of the vertices and edges 
+  * comprising the path from start to info. The returned path is empty if 
+  * info is unreachable from start.  */
+public class FindPathDFS<V, E>
+    extends DFS<V, E, Vertex<V>, Iterable<Position>> {
+  protected PositionList<Position> path;
+  protected boolean done;
+  /** Setup method to initialize the path. */
+  public void setup() {
+    path = new NodePositionList<Position>();
+    done = false;
+  }
+  protected void startVisit(Vertex<V> v) {
+    path.addLast(v); // add vertex v to path
+    if (v == info)
+      done = true;
+  }
+  protected void finishVisit(Vertex<V> v) {
+    path.remove(path.last());	// remove v from path
+    if(!path.isEmpty())		// if v is not the start vertex
+      path.remove(path.last());	// remove discovery edge into v from path
+  }
+  protected void traverseDiscovery(Edge<E> e, Vertex<V> from) {
+    path.addLast(e); // add edge e to the path
+  } 
+  protected boolean isDone() { 
+    return done; 
+  }
+  public Iterable<Position> finalResult(Iterable<Position> r) { 
+    return path;
+  }
+}
+//end#fragment FindPathDFS