/* vim: set expandtab tabstop=4 shiftwidth=4 : */

public class SpecializedBFS
{
    private static final int MAXINT = Integer.MAX_VALUE;

    private boolean[] marked;
    private int[] edgeTo;
    private int[] distTo;

    public SpecializedBFS(Digraph G, int s, ResizingArrayQueue<Integer> c)
    {
        init(G);
        Queue<Integer> q = new Queue<Integer>();
        marked[s] = true;
        distTo[s] = 0;
        q.enqueue(s);
        if (c != null) c.enqueue(s);
        bfs(G, q, c);
    }

    public SpecializedBFS(Digraph G, Iterable<Integer> ss,
            ResizingArrayQueue<Integer> c)
    {
        init(G);
        Queue<Integer> q = new Queue<Integer>();
        for (int s : ss) {
            marked[s] = true;
            distTo[s] = 0;
            q.enqueue(s);
            if (c != null) c.enqueue(s);
        }
        bfs(G, q, c);
    }

    private void init(Digraph g)
    {
        marked = new boolean[g.V()];
        edgeTo = new int[g.V()];
        distTo = new int[g.V()];
        for (int v = 0; v < g.V(); v++)
            distTo[v] = MAXINT;
    }

    public int distTo(int v)
    {
        return distTo[v];
    }

    public boolean hasPathTo(int v)
    {
        return marked[v];
    }

    private void bfs(Digraph G, Queue<Integer> q, ResizingArrayQueue<Integer> c)
    {
        while (!q.isEmpty()) {
            int v = q.dequeue();
            for (int w : G.adj(v)) {
                if (!marked[w]) {
                    edgeTo[w] = v;
                    distTo[w] = distTo[v] + 1;
                    marked[w] = true;
                    q.enqueue(w);
                    if (c != null) c.enqueue(w);
                }
            }
        }
    }

    // change this to an iterator if efficiency is needed
    public Iterable<Integer> pathTo(int v)
    {
        if (!hasPathTo(v)) return null;

        Stack<Integer> path = new Stack<Integer>();
        int x;
        for (x = v; distTo[x] != 0; x = edgeTo[x])
            path.push(x);
        path.push(x);

        return path;
    }

    public int pathToCount(int v)
    {
        if (!hasPathTo(v)) return MAXINT;

        int count = 0;
        for (int x = v; distTo[x] != 0; x = edgeTo[x])
            count++;

        return count;
    }

    public static void main(String[] args)
    {
        In in = new In("./data/digraph3.txt");
        Digraph G = new Digraph(in);
        StdOut.println(G);

        int s = 7;
        ResizingArrayQueue<Integer> components = new ResizingArrayQueue<Integer>();
        SpecializedBFS bfs = new SpecializedBFS(G, s, components);

        for (int v = 0; v < G.V(); v++) {
            if (bfs.hasPathTo(v)) {
                StdOut.printf("%2d -> %2d: [%d]  ", s, v, bfs.distTo(v));
                for (int x : bfs.pathTo(v)) {
                    if (x == s) StdOut.print(x);
                    else        StdOut.print("->" + x);
                }
                StdOut.println();
            } else {
                StdOut.printf("%2d -> %2d: [-]\n", s, v);
            }
        }
        StdOut.printf("components : ");
        for (int c : components) {
            if (c == s) StdOut.print(c);
            else        StdOut.print("->" + c);
        }
        StdOut.print("\n");
        StdOut.printf("pathToCount(%d) : %2d\n", 4, bfs.pathToCount(4));
        StdOut.printf("pathToCount(%d) : %2d\n", 9, bfs.pathToCount(9));

        int s2 = 11;
        SpecializedBFS bfs2 = new SpecializedBFS(G, s2, null);

        for (int v = 0; v < G.V(); v++) {
            if (bfs2.hasPathTo(v)) {
                StdOut.printf("%2d -> %2d: [%d]  ", s2, v, bfs2.distTo(v));
                for (int x : bfs2.pathTo(v)) {
                    if (x == s2) StdOut.print(x);
                    else        StdOut.print("->" + x);
                }
                StdOut.println();
            } else {
                StdOut.printf("%2d -> %2d: [-]\n", s2, v);
            }
        }

        StdOut.printf("intersection : ");
        for (int c : components) {
            if (bfs2.hasPathTo(c))
                    StdOut.print(c+" ");
        }
        StdOut.print("\n");
    }
}