/*
 * Finding a path in a graph
 * 
 * path(X,Y) :- edge(X,Y).
 * path(X,Y) :- edge(X,Z), path(Z,Y).
 * 
 */
import java.util.ArrayList;

public class Path
{
    static private int[][] tree = { {0,1,0,0,0,0},  // 0->1
                                    {0,0,1,0,1,0},  // 1->2, 1->4
                                    {0,0,0,1,1,0},  // 2->3, 2->4
                                    {0,0,0,0,1,0},  // 3->4
                                    {0,0,0,0,0,1},  // 4->5
                                    {0,0,0,0,0,0} };

    public static void main (String[] args)
    {
        System.out.println(findPath(0,5));
    }
    

    public static boolean findPath(int x, int y) 
    {
        boolean found = false;
        if (tree[x][y]==1) 
        {
            System.out.println(x + " -> " + y);
            found = true;
        } 
        else 
        {
            int z;
            for (z=0; !found& z<tree.length; z++) 
            { 
                if (tree[x][z]==1) found = findPath(z,y);
                if (found) System.out.println(x + " -> " + z);
            }
        }
        return found;
    }
    
}

/* Modifications:

 * Use an ArrayList for collecting the path 
   static ArrayList<Integer> path = new ArrayList<Integer>();
   path.add(0,y); // base case
   path.add(0,z);  // recursive call
    
 * Avoid infinite loops. 
   Mark passed nodes (add tree[x][z]=2 before the recursive call)
 * 
 * 
 */