Trees are a special case of a more general data structure known as a directed graph. A graph
consists of nodes and edges, just like in a tree, but the edges can connect any node to any other.
For example, here is a small graph where each node has at most two edges connecting it to other
nodes.
1
17
9
12
25
4
8. For this problem, given a particular node as a starting point, can we reach a node containing a
specific value? In the above example graph, there is a path from the node containing 1 to the
node that contains 12 (1-17-12). There is also a path from the node containing 17 to the node
containing 9 (17-12-4-9). However there is no path from the node containing 12 to the nodes
containing 1 or 17. Finally, there is no path from any node to a node containing 3, since 3
does not appear anywhere in the graph.
You have the task of implementing the method canReach. This method returns true if the
current node contains the specified value or if there is some path from the current node to
some other node that contains the value. Otherwise, it returns false.
Hints: You may assume the instance variable status is set to CLEAR at the beginning of the
search. You may change the value of status as you wish. Be sure you don't get stuck in a
cycle, where you visit a sequence of nodes over and over. Don't panic if the solution turns
out to be relatively short. Partial credit for pseudo-code.
Here is the code for a node:
public class GraphNode {
private int value;
private GraphNode tol, to2;
private int status;
private static final int CLEAR = 0;
private static final int USED = 1;
public boolean canReach (int val) {
