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BreadthFirstSearch.java
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BreadthFirstSearch.java
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import java.util.*;
import java.io.*;
public class BreadthFirstSearch {
class Graph {
private int v; // No. of vertices
private LinkedList<Integer> adj[]; // Adjacency Lists
Graph(int v) {
this.v = v;
adj = new LinkedList[v];
for (int i = 0; i < v; ++i)
adj[i] = new LinkedList<Integer>();
}
void addEdge(int v, int w) {
adj[v].add(w);
adj[w].add(v);
}
// BFS traversal from a given source node 's'
void BFS(int s) {
boolean visited[] = new boolean[v];
// Create a queue for BFS traversal
LinkedList<Integer> queue = new LinkedList<Integer>();
// Mark the current node as visited and add into queue
queue.add(s);
visited[s] = true;
while (!queue.isEmpty()) {
// Remove a vertex from queue and print it
int curr = queue.poll();
System.out.print(curr+ " ");
// Get all adjacent vertices of the dequeued vertex s.
// If an adjacent has not been visited, then mark it visited and enqueue it
for (int nbr : adj[curr]) {
if (!visited[nbr]) {
queue.add(nbr);
visited[nbr] = true;
}
}
}
}
}
public static void main(String args[]) throws IOException {
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
System.out.println("Enter the no. of vertices and edges:");
String[] inp = br.readLine().split(" ");
int N = Integer.parseInt(inp[0]);
int M = Integer.parseInt(inp[1]);
BreadthFirstSearch obj = new BreadthFirstSearch();
Graph g = obj.new Graph(N);
for (int i = 1; i <= M; i++) {
System.out.println("Enter edge No. " + i + ":");
inp = br.readLine().split(" ");
int u = Integer.parseInt(inp[0]);
int v = Integer.parseInt(inp[1]);
g.addEdge(u, v);
}
System.out.println("Enter source vertex: ");
int s = Integer.parseInt(br.readLine());
g.BFS(s);
}
}