package edu.princeton.cs.algs4.ch41;
import edu.princeton.cs.algs4.ch13.Queue;
import edu.princeton.cs.introcs.*;
/*************************************************************************
* 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
*
* % java CC mediumG.txt
* 1 components
* 0 1 2 3 4 5 6 7 8 9 10 ...
*
* % java -Xss50m CC largeG.txt
* 1 components
* 0 1 2 3 4 5 6 7 8 9 10 ...
*
*************************************************************************/
/**
* The <tt>CC</tt> class represents a data type for
* determining the connected components in an undirected graph.
* The <em>id</em> operation determines in which connected component
* a given vertex lies; the <em>connected</em> operation
* determines whether two vertices are in the same connected component;
* the <em>count</em> operation determines the number of connected
* components; and the <em>size</em> operation determines the number
* of vertices in the connect component containing a given vertex.
* The <em>component identifier</em> of a connected component is one of the
* vertices in the connected component: two vertices have the same component
* identifier if and only if they are in the same connected component.
* <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.
* Afterwards, the <em>id</em>, <em>count</em>, <em>connected</em>,
* and <em>size</em> operations take constant time.
* <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 CC {
private boolean[] marked; // marked[v] = has vertex v been marked?
private int[] id; // id[v] = id of connected component containing v
private int[] size; // size[id] = number of vertices in given component
private int count; // number of connected components
/**
* Computes the connected components of the undirected graph <tt>G</tt>.
* @param G the graph
*/
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);
}
}
}
/**
* Returns the component id of the connected component containing vertex <tt>v</tt>.
* @param v the vertex
* @return the component id of the connected component containing vertex <tt>v</tt>
*/
public int id(int v) {
return id[v];
}
/**
* Returns the number of vertices in the connected component containing vertex <tt>v</tt>.
* @param v the vertex
* @return the number of vertices in the connected component containing vertex <tt>v</tt>
*/
public int size(int v) {
return size[id[v]];
}
/**
* Returns the number of connected components.
* @return the number of connected components
*/
public int count() {
return count;
}
/**
* Are vertices <tt>v</tt> and <tt>w</tt> in the same connected component?
* @param v one vertex
* @param w the other vertex
* @return <tt>true</tt> if vertices <tt>v</tt> and <tt>w</tt> are in the same
* connected component, and <tt>false</tt> otherwise
*/
public boolean connected(int v, int w) {
return id(v) == id(w);
}
/**
* Are vertices <tt>v</tt> and <tt>w</tt> in the same connected component?
* @param v one vertex
* @param w the other vertex
* @return <tt>true</tt> if vertices <tt>v</tt> and <tt>w</tt> are in the same
* connected component, and <tt>false</tt> otherwise
* @deprecated Use connected(v, w) instead.
*/
public boolean areConnected(int v, int w) {
return id(v) == id(w);
}
/**
* Unit tests the <tt>CC</tt> data type.
*/
public static void main(String[] args) {
In in = new In(args[0]);
Graph G = new Graph(in);
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
Queue<Integer>[] components = (Queue<Integer>[]) new Queue[M];
for (int i = 0; i < M; i++) {
components[i] = new Queue<Integer>();
}
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();
}
}
}
/*************************************************************************
* 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.
*************************************************************************/