package edu.princeton.cs.algs4.ch41;
import edu.princeton.cs.introcs.*;
/*************************************************************************
* 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
*
*************************************************************************/
/**
* The <tt>DepthFirstSearch</tt> class represents a data type for
* determining the vertices connected to a given source vertex <em>s</em>
* in an undirected graph. For versions that find the paths, see
* {@link DepthFirstPaths} and {@link BreadthFirstPaths}.
* <p>
* This implementation uses depth-first search.
* The constructor takes time proportional to <em>V</em> + <em>E</em>
* (in the worst case),
* where <em>V</em> is the number of vertices and <em>E</em> is the number of edges.
* It uses extra space (not including the graph) proportional to <em>V</em>.
* <p>
* For additional documentation, see <a href="/algs4/41graph">Section 4.1</a> of
* <i>Algorithms, 4th Edition</i> by Robert Sedgewick and Kevin Wayne.
*
* @author Robert Sedgewick
* @author Kevin Wayne
*/
public class DepthFirstSearch {
private boolean[] marked; // marked[v] = is there an s-v path?
private int count; // number of vertices connected to s
/**
* Computes the vertices in graph <tt>G</tt> that are
* connected to the source vertex <tt>s</tt>.
* @param G the graph
* @param s the source vertex
*/
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) {
count++;
marked[v] = true;
for (int w : G.adj(v)) {
if (!marked[w]) {
dfs(G, w);
}
}
}
/**
* Is there a path between the source vertex <tt>s</tt> and vertex <tt>v</tt>?
* @param v the vertex
* @return <tt>true</tt> if there is a path, <tt>false</tt> otherwise
*/
public boolean marked(int v) {
return marked[v];
}
/**
* Returns the number of vertices connected to the source vertex <tt>s</tt>.
* @return the number of vertices connected to the source vertex <tt>s</tt>
*/
public int count() {
return count;
}
/**
* Unit tests the <tt>DepthFirstSearch</tt> data type.
*/
public static void main(String[] args) {
In in = new In(args[0]);
Graph G = new Graph(in);
int s = Integer.parseInt(args[1]);
DepthFirstSearch search = new DepthFirstSearch(G, s);
for (int v = 0; v < G.V(); v++) {
if (search.marked(v))
StdOut.print(v + " ");
}
StdOut.println();
if (search.count() != G.V()) StdOut.println("NOT connected");
else StdOut.println("connected");
}
}
/*************************************************************************
* Copyright 2002-2012, Robert Sedgewick and Kevin Wayne.
*
* This file is part of algs4-package.jar, which accompanies the textbook
*
* Algorithms, 4th edition by Robert Sedgewick and Kevin Wayne,
* Addison-Wesley Professional, 2011, ISBN 0-321-57351-X.
* http://algs4.cs.princeton.edu
*
*
* algs4-package.jar is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* algs4-package.jar is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
* You should have received a copy of the GNU General Public License
* along with algs4-package.jar. If not, see http://www.gnu.org/licenses.
*************************************************************************/