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DFS.java
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123 lines (103 loc) · 3.2 KB
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package graph;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.Scanner;
/**
* @author Sesh Venugopal.
*/
class Neighbor {
public int vertexNum;
public Neighbor next;
public Neighbor(int vnum, Neighbor nbr) {
this.vertexNum = vnum;
next = nbr;
}
}
class Vertex {
String name;
Neighbor adjList;
Vertex(String name, Neighbor neighbors) {
this.name = name;
this.adjList = neighbors;
}
}
class Graph {
Vertex[] adjLists; // Keys
public Graph(String file) throws FileNotFoundException {
Scanner sc = new Scanner(new File(file));
String graphType = sc.next();
boolean undirected=true;
if (graphType.equals("directed")) {
undirected=false;
}
adjLists = new Vertex[sc.nextInt()];
// read vertices
for (int v=0; v < adjLists.length; v++) {
adjLists[v] = new Vertex(sc.next(), null);
}
// read edges
while (sc.hasNext()) {
// read vertex names and translate to vertex numbers
int v1 = indexForName(sc.next());
int v2 = indexForName(sc.next());
// add v2 to front of v1's adjacency list and
// add v1 to front of v2's adjacency list
adjLists[v1].adjList = new Neighbor(v2, adjLists[v1].adjList);
if (undirected) {
adjLists[v2].adjList = new Neighbor(v1, adjLists[v2].adjList);
}
}
}
int indexForName(String name) {
for (int v=0; v < adjLists.length; v++) {
if (adjLists[v].name.equals(name)) {
return v;
}
}
return -1;
}
// recursive dfs
private void dfs(int v, boolean[] visited) {
visited[v] = true;
System.out.println("visiting " + adjLists[v].name);
for (Neighbor nbr=adjLists[v].adjList; nbr != null; nbr=nbr.next) {
if (!visited[nbr.vertexNum]) {
System.out.println("\n" + adjLists[v].name + "--" + adjLists[nbr.vertexNum].name);
dfs(nbr.vertexNum, visited);
}
}
}
public void dfs() {
boolean[] visited = new boolean[adjLists.length];
for (int v=0; v < visited.length; v++) {
if (!visited[v]) {
System.out.println("\nSTARTING AT " + adjLists[v].name);
dfs(v, visited);
}
}
}
public void print() {
System.out.println();
for (int v=0; v < adjLists.length; v++) {
System.out.print(adjLists[v].name);
for (Neighbor nbr=adjLists[v].adjList; nbr != null;nbr=nbr.next) {
System.out.print(" --> " + adjLists[nbr.vertexNum].name);
}
System.out.println("\n");
}
}
/**
* @param args
*/
public static void main(String[] args)
throws IOException {
// TODO Auto-generated method stub
Scanner sc = new Scanner(System.in);
System.out.print("Enter graph input file name: ");
String file = sc.nextLine();
Graph graph = new Graph(file);
//graph.print();
graph.dfs();
}
}