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[Function add]
1. Add the reacheable method for directed graph using depth first search.
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Diff for: ‎Algorithm(4th_Edition)/src/ca/mcmaster/chapter/four/graph/DirectedDFS.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 DirectedDFS {
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private final boolean[] marked;
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public DirectedDFS(Digraph g, int s){
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this.marked = new boolean[g.V()];
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dfs(g, s);
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}
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public DirectedDFS(Digraph g, Iterable<Integer> sources){
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marked = new boolean[g.V()];
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for(int s : sources)
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if(!marked[s]) dfs(g, s);
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}
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private void dfs(Digraph g, int s) {
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marked[s] = true;
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for(int w : g.adj(s))
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if(!marked[w]) dfs(g, w);
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}
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public boolean mark(int v){
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return marked[v];
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}
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public static void main(String[] args) throws FileNotFoundException {
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Digraph g = new DigraphImpl(new FileInputStream(new File("src/ca/mcmaster/chapter/four/graph/tinyDG.txt")));
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Bag<Integer> bag = new ListBag<Integer>();
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bag.add(1);
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bag.add(2);
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bag.add(6);
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DirectedDFS d = new DirectedDFS(g, bag);
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StringBuilder sb = new StringBuilder();
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for(int v = 0; v < g.V(); v++){
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if(d.mark(v)) sb.append(v + " ");
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}
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System.out.println(sb.toString());
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}
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}

Diff for: ‎DataStructrue/Graph/Digraph.java

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package ca.mcmaster.chapter.four.graph;
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public interface Digraph {
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/**
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* @Description: Number of vertex.
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* @return
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*/
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public int V();
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/**
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* @Description: Number of edge.
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* @return
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*/
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public int E();
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/**
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* @Description: Add an edge between two vertex. v->w.
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* @param v
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* @param w
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*/
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public void addEdge(int v, int w);
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/**
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* @Description: Return vertex point out from v.
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* @param v
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* @return
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*/
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public Iterable<Integer> adj(int v);
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/**
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* @Description: Get the reverse graph of current graph.
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* @return
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*/
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public Digraph reverse();
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/**
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* @Description: Print current graph.
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*/
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public void display();
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}

Diff for: ‎DataStructrue/Graph/DigraphImpl.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.IOException;
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import java.util.Scanner;
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import ca.mcmaster.chapter.one.bag.ListBag;
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public class DigraphImpl implements Digraph {
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private final int V; //Number of vertex in current digraph
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private int E; //Number of edges.
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private ListBag<Integer>[] adj;
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@SuppressWarnings("unchecked")
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public DigraphImpl(int V){
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this.V = V;
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adj = (ListBag<Integer>[])new ListBag[V];
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for (int i = 0; i < V; i++) {
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adj[i] = new ListBag<Integer>();
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}
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this.E = 0;
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}
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@SuppressWarnings("unchecked")
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public DigraphImpl(FileInputStream in) {
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Scanner s = null;
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s = new Scanner(in);
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this.V = s.nextInt();
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this.E = s.nextInt();
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adj = new ListBag[V];
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for (int i = 0; i < V; i++) {
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adj[i] = new ListBag<Integer>();
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}
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for(int i = 0; i < E; i ++){
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int v = s.nextInt();
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int w = s.nextInt();
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adj[v].add(w);
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}
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s.close();
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}
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@Override
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public int V() { return this.V; }
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@Override
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public void addEdge(int v, int w) {
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adj[v].add(w);
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E++;
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}
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@Override
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public int E() { return E; }
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@Override
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public Iterable<Integer> adj(int v) {
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return adj[v];
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}
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@Override
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public Digraph reverse() {
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DigraphImpl g = new DigraphImpl(V);
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for(int v = 0; v < V; v++)
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for(int w : adj(v))
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addEdge(w, v);
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return g;
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}
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@Override
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public void display() {
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for(int i = 0; i < V; i++){
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StringBuilder sb = new StringBuilder(i + ": ");
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for(int w : adj[i]){
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sb.append(w + "|");
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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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public static void main(String[] args) throws IOException {
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FileInputStream in = new FileInputStream(new File("src/ca/mcmaster/chapter/four/graph/tinyDG.txt"));
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Digraph graph = new DigraphImpl(in);
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in.close();
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graph.display();
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}
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}

Diff for: ‎DataStructrue/Graph/DirectedDFS.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 DirectedDFS {
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private final boolean[] marked;
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public DirectedDFS(Digraph g, int s){
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this.marked = new boolean[g.V()];
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dfs(g, s);
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}
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public DirectedDFS(Digraph g, Iterable<Integer> sources){
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marked = new boolean[g.V()];
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for(int s : sources)
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if(!marked[s]) dfs(g, s);
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}
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private void dfs(Digraph g, int s) {
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marked[s] = true;
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for(int w : g.adj(s))
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if(!marked[w]) dfs(g, w);
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}
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public boolean mark(int v){
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return marked[v];
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}
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public static void main(String[] args) throws FileNotFoundException {
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Digraph g = new DigraphImpl(new FileInputStream(new File("src/ca/mcmaster/chapter/four/graph/tinyDG.txt")));
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Bag<Integer> bag = new ListBag<Integer>();
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bag.add(1);
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bag.add(2);
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bag.add(6);
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DirectedDFS d = new DirectedDFS(g, bag);
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StringBuilder sb = new StringBuilder();
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for(int v = 0; v < g.V(); v++){
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if(d.mark(v)) sb.append(v + " ");
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}
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System.out.println(sb.toString());
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}
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}

Diff for: ‎DataStructrue/Graph/DirectedGraph.md

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>10: 12|
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>11: 4|12|
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>12: 9|
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### 有向图的可达性
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```Java
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public class DirectedDFS {
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private final boolean[] marked;
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public DirectedDFS(Digraph g, int s){
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this.marked = new boolean[g.V()];
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dfs(g, s);
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}
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public DirectedDFS(Digraph g, Iterable<Integer> sources){
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marked = new boolean[g.V()];
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for(int s : sources)
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if(!marked[s]) dfs(g, s);
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}
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private void dfs(Digraph g, int s) {
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marked[s] = true;
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for(int w : g.adj(s))
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if(!marked[w]) dfs(g, w);
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}
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public boolean mark(int v){
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return marked[v];
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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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Digraph g = new DigraphImpl(new FileInputStream(new File("src/ca/mcmaster/chapter/four/graph/tinyDG.txt")));
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Bag<Integer> bag = new ListBag<Integer>();
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bag.add(1);
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bag.add(2);
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bag.add(6);
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DirectedDFS d = new DirectedDFS(g, bag);
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StringBuilder sb = new StringBuilder();
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for(int v = 0; v < g.V(); v++){
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if(d.mark(v)) sb.append(v + " ");
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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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