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Java

A traversal code using Breadth First Search.

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  • Main.java
Main.java
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import java.util.LinkedList;

public class Main {

    /*To represent number of vertices*/
    private int Vertices;

    /*To represent adjacency lists*/
    private LinkedList<Integer>[] adjacent;

    /*Default constructor*/
    private Main(int vertex) {
        Vertices = vertex;
        adjacent = new LinkedList[vertex];
        for (int i = 0; i < vertex; i++)
            adjacent[i] = new LinkedList();
    }

    /*Driver method*/
    public static void main(String[] args) {
        Main g = new Main(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);
    }

    /*Adding an edge to a particular list*/
    private void addEdge(int vertex, int edge) {
        adjacent[vertex].add(edge);
    }

    /*This is gonna traverse a graph by the help of BFS*/
    private void BFS(int source) {

        /*To check if a vertex is visited or not, initially zero or not visited*/
        boolean[] visited = new boolean[Vertices];

        /*Queue for checking each layer of data*/
        LinkedList<Integer> queue = new LinkedList<Integer>();

        /*Marking source/current node/vertex as visited*/
        visited[source] = true;
        queue.add(source);

        while (queue.size() != 0) {

            /*Printing the traversing vertex.
             * If one want's to make this BFS as just for searching a particular value,
             * he needs to change this.*/
            source = queue.poll();
            System.out.println("Pulled out: " + source);

            /*Iterating over the sources adjacent vertices and adding them over queue*/
            for (int n : adjacent[source]) {
                if (!visited[n]) {
                    visited[n] = true;
                    queue.add(n);
                }
            }
        }
    }
}
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