package algs41;
import stdlib.*;
/* ***********************************************************************
 *  Compilation:  javac DepthFirstSearch.java
 *  Execution:    java DepthFirstSearch filename.txt s
 *  Dependencies: Graph.java StdOut.java
 *  Data files:   http://algs4.cs.princeton.edu/41undirected/tinyG.txt
 *
 *  Run depth first search on an undirected graph.
 *  Runs in O(E + V) time.
 *
 *  % java DepthFirstSearch tinyG.txt 0
 *  0 1 2 3 4 5 6
 *  NOT connected
 *
 *  % java DepthFirstSearch tinyG.txt 9
 *  9 10 11 12
 *  NOT connected
 *
 *************************************************************************/

public class DepthFirstSearch {
  private final boolean[] marked;    // marked[v] = is there an s-v path?
  private int count;                 // number of vertices connected to s

  // single source
  public DepthFirstSearch(Graph G, int s) {
    marked = new boolean[G.V()];
    dfs(G, s);
  }

  // depth first search from v
  private void dfs(Graph G, int v) {
    //StdOut.printf ("visited %d\n", v);
    marked[v] = true;
    count++;
    for (int w : G.adj(v)) {
      if (!marked[w]) {
        dfs(G, w);
      }
    }
  }

  // using an explicit stack
  private void dfsLoop1(Graph G, int v) {
    algs13.Stack<Integer> s = new algs13.Stack<>();
    s.push (v);
    marked[v] = true;
    count++;
    while (!s.isEmpty ()) {
      v = s.pop ();
      StdOut.printf ("visited %d\n", v);
      for (int w : G.adj(v)) {
        if (!marked[w]) {
          s.push (w);
          marked[w] = true;
          count++;
        }
      }
    }
  }

  // Use tmp stack to get nodes in same order as recursive version
  private void dfsLoop2(Graph G, int v) {
    algs13.Stack<Integer> s = new algs13.Stack<>();
    s.push (v);
    marked[v] = true;
    count++;
    while (!s.isEmpty ()) {
      v = s.pop ();
      StdOut.printf ("visited %d\n", v);
      algs13.Stack<Integer> tmp= new algs13.Stack<>();
      for (int w : G.adj(v)) {
        if (!marked[w]) {
          tmp.push (w);
          marked[w] = true;
          count++;
        }
      }
      while (!tmp.isEmpty ()) { s.push (tmp.pop ());}
    }
  }

  // is there an s-v path?
  public boolean marked(int v) {
    return marked[v];
  }

  // number of vertices connected to s
  public int count() {
    return count;
  }

  // test client
  public static void main(String[] args) {
    args = new String [] { "data/tinyG.txt", "0" };
    //args = new String [] { "data/tinyCG.txt", "0" };

    In in = new In(args[0]);
    Graph G = GraphGenerator.fromIn (in);
    StdOut.println (G);

    int s = Integer.parseInt(args[1]);
    DepthFirstSearch search = new DepthFirstSearch(G, s);

    StdOut.print("Marked=");
    for (int v = 0; v < G.V(); v++) {
      if (search.marked(v))
        StdOut.print(v + " ");
    }

    StdOut.println();
    StdOut.println("Count=" + search.count ());
    if (search.count() != G.V()) StdOut.println("NOT connected");
    else                         StdOut.println("connected");
  }

}