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BFS.java
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162 lines (137 loc) · 3.52 KB
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package graph.bfs;
//undirected
//10
//Sara
//Sam
//Sean
//Ajay
//Mira
//Jane
//Maria
//Rahul
//Sapna
//Rohit
//Sara Sam
//Sara Ajay
//Sam Sean
//Sam Mira
//Mira Jane
//Jane Maria
//Rahul Sapna
//Sapna Rohit
// directed
//6
//PageA
//PageB
//PageC
//PageD
//PageE
//PageF
//PageA PageB
//PageA PageD
//PageA PageE
//PageB PageD
//PageC PageA
//PageD PageB
//PageE PageF
//PageF PageD
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.Scanner;
//import linear.Queue;
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;
}
}
/**
* @author Sesh Venugopal.
*/
class Graph {
Vertex[] adjLists;
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;
}
public void bfs() {
boolean[] visited = new boolean[adjLists.length];
Queue<Integer> queue = new Queue<Integer>();
for (int v=0; v < visited.length; v++) {
if (!visited[v]) {
System.out.println("\nSTARTING AT " + adjLists[v].name);
queue.clear();
bfs(v, visited, queue);
}
}
}
// BFS starting at some vertex v
private void bfs(int start, boolean[] visited, Queue<Integer> queue) {
visited[start] = true;
System.out.println("visiting " + adjLists[start].name);
queue.enqueue(start);
while (!queue.isEmpty()) {
int v = queue.dequeue();
for (Neighbor nbr=adjLists[v].adjList; nbr != null; nbr=nbr.next) {
int vnum = nbr.vertexNum;
if (!visited[vnum]) {
System.out.println("\n" + adjLists[v].name + "--" + adjLists[vnum].name);
visited[vnum] = true;
queue.enqueue(vnum);
}
}
}
}
/**
* @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.bfs();
}
}