package algs41;
import stdlib.*;
import algs13.Queue;
/* ***********************************************************************
 *  Compilation:  javac CC.java
 *  Execution:    java CC filename.txt
 *  Dependencies: Graph.java StdOut.java Queue.java
 *  Data files:   http://algs4.cs.princeton.edu/41undirected/tinyG.txt
 *
 *  Compute connected components using depth first search.
 *  Runs in O(E + V) time.
 *
 *  %  java CC tinyG.txt
 *  3 components
 *  0 1 2 3 4 5 6
 *  7 8
 *  9 10 11 12
 *
 *************************************************************************/

public class CC {
  private final boolean[] marked;   // marked[v] = has vertex v been marked?
  private final int[] id;           // id[v] = id of connected component containing v
  private final int[] size;         // size[id] = number of vertices in component containing v
  private int count;                // number of connected components

  public CC(Graph G) {
    marked = new boolean[G.V()];
    id = new int[G.V()];
    size = new int[G.V()];
    for (int v = 0; v < G.V(); v++) {
      if (!marked[v]) {
        dfs(G, v);
        count++;
      }
    }
  }

  // depth first search
  private void dfs(Graph G, int v) {
    marked[v] = true;
    id[v] = count;
    size[count]++;
    for (int w : G.adj(v)) {
      if (!marked[w]) {
        dfs(G, w);
      }
    }
  }

  // id of connected component containing v
  public int id(int v) {
    return id[v];
  }

  // size of connected component containing v
  public int size(int v) {
    return size[id[v]];
  }

  // number of connected components
  public int count() {
    return count;
  }

  // are v and w in the same connected component?
  public boolean areConnected(int v, int w) {
    return id(v) == id(w);
  }


  // test client
  public static void anotherTest() {
    Graph G;
    do {
      G = GraphGenerator.simple(20,40);
    } while (new CC(G).count() != 1);
    G.toGraphviz ("g.png");
  }
  public static void main(String[] args) {
    anotherTest();
//    args = new String [] { "10", "5" };
//    final int V = Integer.parseInt(args[0]);
//    final int E = Integer.parseInt(args[1]);
//    final Graph G = GraphGenerator.simple(V, E);
//    StdOut.println(G);

    //args = new String [] { "data/tinyAG.txt" };
    args = new String [] { "data/tinyG.txt" };
    In in = new In(args[0]);
    Graph G = GraphGenerator.fromIn (in);
    StdOut.println(G);
    G.toGraphviz ("g");
    
    CC cc = new CC(G);

    // number of connected components
    int M = cc.count();
    StdOut.println(M + " components");

    // compute list of vertices in each connected component
    @SuppressWarnings("unchecked")
    Queue<Integer>[] components = new Queue[M];
    for (int i = 0; i < M; i++) {
      components[i] = new Queue<>();
    }
    for (int v = 0; v < G.V(); v++) {
      components[cc.id(v)].enqueue(v);
    }

    // print results
    for (int i = 0; i < M; i++) {
      for (int v : components[i]) {
        StdOut.print(v + " ");
      }
      StdOut.println();
    }
  }
}