public class Reachability {
    private int numNodes;
    private int[][] arcs;

    public Reachability(int numNodes) {
        this.numNodes = numNodes;
        arcs = new int[numNodes][];
    }
    public int getNumNodes() {
        return numNodes;
    }
    public int getNumArcs(int node) {
        return arcs[node].length;
    }
    public void setNumArcs(int node, int numArcs) {
        arcs[node] = new int[numArcs];
    }
    public void setArcs(int node, int arc, int target) {
        arcs[node][arc] = target;
    }
    public boolean[] calcReachability(int node) {
        boolean[] reachable = new boolean[numNodes]; // the reachable nodes
        reachable[node] = true;                      // initially just me
        calcReachabilityHelper(node, reachable);
        return reachable;
    }
    private void calcReachabilityHelper(int node, boolean[] reachable) {
        for (int i=0; i<arcs[node].length; i++) {   // for all successors
            int successor = arcs[node][i];
            if (!reachable[successor]) {  // if successor not marked reachable
                reachable[successor] = true;  // mark it reachable and
                calcReachabilityHelper(successor, reachable); //  process it
            }
        }
    }
    public void printArcs() {
        for (int i=0; i<numNodes; i++){
            System.out.print(i + ": ");
            for (int j=0; j<arcs[i].length; j++)
                System.out.print(arcs[i][j] + " ");
            System.out.println();
        }
    }
    public void printReachability(int node, boolean[] reachable) {
        System.out.print(node + ": ");
        for (int i=0; i<numNodes; i++)
            if (reachable[i])
                System.out.print(i + " ");
        System.out.println();
    }    
}
// Local Variables:
// c-basic-offset: 4
// compile-command: "javac DemoReachability.java"
// End: