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[Function add]
1.Add connection component based on DFS.
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‎Algorithm(4th_Edition)/src/ca/mcmaster/chapter/four/graph/AbstractCC.java

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package ca.mcmaster.chapter.four.graph;
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public abstract class AbstractCC implements ConnectionComponent {
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protected final Graph g;
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public AbstractCC(Graph g){
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this.g = g;
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}
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}

‎Algorithm(4th_Edition)/src/ca/mcmaster/chapter/four/graph/ConnectionComponent.java

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package ca.mcmaster.chapter.four.graph;
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public interface ConnectionComponent {
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/**
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* @Description: If v and w are connected.
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* @param v
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* @param w
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* @return
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*/
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public boolean connected(int v, int w);
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/**
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* @Description: Number of cc in current graph.
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* @return
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*/
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public int count();
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/**
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* @Description: Identification of connection component.
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* @param v
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* @return
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*/
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public int id(int v);
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}

‎Algorithm(4th_Edition)/src/ca/mcmaster/chapter/four/graph/DFSCC.java

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package ca.mcmaster.chapter.four.graph;
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import java.io.File;
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import java.io.FileInputStream;
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import java.io.FileNotFoundException;
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import ca.mcmaster.chapter.one.bag.Bag;
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import ca.mcmaster.chapter.one.bag.ListBag;
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public class DFSCC extends AbstractCC {
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private boolean[] marked;
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private int[] id;
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private int count;
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public DFSCC(Graph g) {
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super(g);
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marked = new boolean[g.V()];
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id = new int[g.V()];
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for(int v = 0; v < g.V(); v++)
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if(!marked[v]){ //Current vertex is not accessed.
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dfs(g, v);
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count++;
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}
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}
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@Override
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public boolean connected(int v, int w) {
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return id[w] == id[v];
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}
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@Override
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public int count() {
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return this.count;
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}
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@Override
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public int id(int v) {
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return id[v];
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}
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private void dfs(Graph g, int v){
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marked[v] = true;
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id[v] = count;
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for(int w : g.adj(v))
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if(!marked[w])
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dfs(g, w);
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}
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@SuppressWarnings("unchecked")
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public static void main(String[] args) throws FileNotFoundException {
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Graph g = new UndirectedGraph(new FileInputStream(new File("src/ca/mcmaster/chapter/four/graph/tinyG.txt")));
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DFSCC cc = new DFSCC(g);
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int ccNum = cc.count();
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System.out.println("Number of cc: " + ccNum);
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Bag<Integer>[] bag = new ListBag[ccNum];
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for(int i = 0; i < ccNum; i++)
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bag[i] = new ListBag<>();
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for(int i = 0; i < g.V(); i++)
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bag[cc.id(i)].add(i);
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for(int i = 0; i < ccNum; i++){
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StringBuilder sb = new StringBuilder(i + ": ");
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for(int v : bag[i])
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sb.append(v + " ");
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System.out.println(sb.toString());
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}
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}
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}

‎DataStructrue/Graph/AbstractCC.java

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package ca.mcmaster.chapter.four.graph;
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public abstract class AbstractCC implements ConnectionComponent {
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protected final Graph g;
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public AbstractCC(Graph g){
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this.g = g;
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}
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}

‎DataStructrue/Graph/ConnectionComponent.java

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package ca.mcmaster.chapter.four.graph;
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public interface ConnectionComponent {
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/**
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* @Description: If v and w are connected.
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* @param v
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* @param w
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* @return
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*/
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public boolean connected(int v, int w);
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/**
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* @Description: Number of cc in current graph.
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* @return
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*/
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public int count();
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/**
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* @Description: Identification of connection component.
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* @param v
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* @return
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*/
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public int id(int v);
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}

‎DataStructrue/Graph/DFSCC.java

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package ca.mcmaster.chapter.four.graph;
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import java.io.File;
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import java.io.FileInputStream;
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import java.io.FileNotFoundException;
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import ca.mcmaster.chapter.one.bag.Bag;
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import ca.mcmaster.chapter.one.bag.ListBag;
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public class DFSCC extends AbstractCC {
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private boolean[] marked;
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private int[] id;
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private int count;
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public DFSCC(Graph g) {
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super(g);
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marked = new boolean[g.V()];
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id = new int[g.V()];
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for(int v = 0; v < g.V(); v++)
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if(!marked[v]){ //Current vertex is not accessed.
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dfs(g, v);
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count++;
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}
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}
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@Override
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public boolean connected(int v, int w) {
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return id[w] == id[v];
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}
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@Override
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public int count() {
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return this.count;
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}
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@Override
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public int id(int v) {
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return id[v];
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}
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private void dfs(Graph g, int v){
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marked[v] = true;
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id[v] = count;
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for(int w : g.adj(v))
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if(!marked[w])
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dfs(g, w);
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}
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@SuppressWarnings("unchecked")
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public static void main(String[] args) throws FileNotFoundException {
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Graph g = new UndirectedGraph(new FileInputStream(new File("src/ca/mcmaster/chapter/four/graph/tinyG.txt")));
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DFSCC cc = new DFSCC(g);
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int ccNum = cc.count();
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System.out.println("Number of cc: " + ccNum);
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Bag<Integer>[] bag = new ListBag[ccNum];
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for(int i = 0; i < ccNum; i++)
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bag[i] = new ListBag<>();
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for(int i = 0; i < g.V(); i++)
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bag[cc.id(i)].add(i);
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for(int i = 0; i < ccNum; i++){
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StringBuilder sb = new StringBuilder(i + ": ");
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for(int v : bag[i])
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sb.append(v + " ");
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System.out.println(sb.toString());
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}
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}
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}

‎DataStructrue/Graph/UndirectedGraph.md

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}
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System.out.println(sb.toString());
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}
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```
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```
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### 连通分量 Connection Component
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>无向图G的极大连通子图称为G的连通分量( Connected Component)。任何连通图的连通分量只有一个，即是其自身，非连通的无向图有多个连通分量。
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* 接口
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```Java
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public interface ConnectionComponent {
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/**
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* @Description: If v and w are connected.
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* @param v
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* @param w
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* @return
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*/
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public boolean connected(int v, int w);
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/**
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* @Description: Number of cc in current graph.
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* @return
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*/
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public int count();
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/**
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* @Description: Identification of connection component.
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* @param v
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* @return
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*/
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public int id(int v);
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}
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```
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* 抽象类
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```Java
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public abstract class AbstractCC implements ConnectionComponent {
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protected final Graph g;
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public AbstractCC(Graph g){
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this.g = g;
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}
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}
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```
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* 基于DFS的实现
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```Java
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public class DFSCC extends AbstractCC {
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private boolean[] marked;
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private int[] id;
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private int count;
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public DFSCC(Graph g) {
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super(g);
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marked = new boolean[g.V()];
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id = new int[g.V()];
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for(int v = 0; v < g.V(); v++) //Traversal all of vertex if not accessed
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if(!marked[v]){ //Current vertex is not accessed.
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dfs(g, v);
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count++;
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}
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}
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@Override
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public boolean connected(int v, int w) {
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return id[w] == id[v];
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}
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@Override
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public int count() {
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return this.count;
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}
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@Override
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public int id(int v) {
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return id[v];
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}
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private void dfs(Graph g, int v){
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marked[v] = true;
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id[v] = count; //assign current count to this vertex as id.
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for(int w : g.adj(v))
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if(!marked[w])
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dfs(g, w);
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}
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}
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```
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* 测试
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```Java
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public static void main(String[] args) throws FileNotFoundException {
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Graph g = new UndirectedGraph(new FileInputStream(new File("src/ca/mcmaster/chapter/four/graph/tinyG.txt")));
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DFSCC cc = new DFSCC(g);
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int ccNum = cc.count();
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System.out.println("Number of cc: " + ccNum);
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Bag<Integer>[] bag = new ListBag[ccNum]; //Create bag array to save all connection components.
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for(int i = 0; i < ccNum; i++)
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bag[i] = new ListBag<>();
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for(int i = 0; i < g.V(); i++)
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bag[cc.id(i)].add(i); //Add vertex into bag.
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for(int i = 0; i < ccNum; i++){
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StringBuilder sb = new StringBuilder(i + ": ");
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for(int v : bag[i])
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sb.append(v + " ");
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System.out.println(sb.toString());
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}
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}
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```
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> Number of cc: 3
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> 0: 6 5 4 3 2 1 0
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> 1: 8 7
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> 2: 12 11 10 9

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