Breadth First Search [BFS]
BFS algorithm works similar to level-order traversal of the tree.
- BFS also uses queues.
- Initially, BFS starts at a given vertex, which is at level 0.
- In the first stage, it visits all vertices at level 1.
- In the second stage, it visits all vertices at level 2.
Source code in Java:
import java.util.LinkedList;
import java.util.Iterator;
/**
*
* @author Rohan
*/
public class Graph
{
private int V; // No. of vertices
// Array of lists for Adjacency List Representation
private LinkedList<Integer> adj[];
// Constructor
Graph(int v)
{
V = v;
adj = new LinkedList[v];
for (int i=0; i<v; ++i)
adj[i] = new LinkedList();
}
//Function to add an edge into the graph
void addEdge(int v, int w)
{
adj[v].add(w); // Add w to v's list.
}
// prints BFS traversal from a given source s
void BFS(int s)
{
// Mark all the vertices as not visited(By default
// set as false)
boolean visited[] = new boolean[V];
// Create a queue for BFS
LinkedList<Integer> queue = new LinkedList<Integer>();
// Mark the current node as visited and enqueue it
visited[s]=true;
queue.add(s);
while (queue.size() != 0)
{
// Dequeue a vertex from queue and print it
s = queue.poll();
System.out.print(s+" ");
// Get all adjacent vertices of the dequeued vertex s
// If a adjacent has not been visited, then mark it
// visited and enqueue it
Iterator<Integer> i = adj[s].listIterator();
while (i.hasNext())
{
int n = i.next();
if (!visited[n])
{
visited[n] = true;
queue.add(n);
}
}
}
}
public static void main(String args[])
{
Graph g = new Graph(4);
g.addEdge(0, 1);
g.addEdge(0, 2);
g.addEdge(1, 2);
g.addEdge(2, 0);
g.addEdge(2, 3);
g.addEdge(3, 3);
System.out.println("Following is Breadth First Traversal "+
"(starting from vertex 2)");
g.BFS(2);
}
}
Output:
Following is Breadth-First Traversal (starting from vertex 2)
2 0 3 1
Explanation:
Comments
Post a Comment