graph = {

  '5' : ['3','7'],

  '3' : ['2', '4'],

  '7' : ['8'],

  '2' : [],

  '4' : ['8'],

  '8' : []

}

​

visited = [] # List for visited nodes.

queue = []     #Initialize a queue

​

def bfs(visited, graph, node): #function for BFS

  visited.append(node)

  queue.append(node)

​

  while queue:          # Creating loop to visit each node

    m = queue.pop(0) 

    print (m, end = " ") 

​

    for neighbour in graph[m]:

      if neighbour not in visited:

        visited.append(neighbour)

        queue.append(neighbour)

​

# Driver Code

print("Following is the Breadth-First Search")

bfs(visited, graph, '5')    # function calling

remember for breadth first searches, you are putting the vertex of your graph into a queue and that determines the order they are travelled

import java.util.*;

​

public class BreadthFirstSearch {

​

    public static void main(String[] args) {

        int numVertices = 7;

        List<List<Integer>> graph = new ArrayList<>();

​

        // Initialize the graph

        for (int i = 0; i < numVertices; i++) {

            graph.add(new ArrayList<>());

        }

​

        // Add edges

        addEdge(graph, 0, 1);

        addEdge(graph, 0, 2);

        addEdge(graph, 1, 3);

        addEdge(graph, 1, 4);

        addEdge(graph, 2, 5);

        addEdge(graph, 2, 6);

​

        // Perform BFS traversal

        System.out.println("BFS Traversal:");

        bfs(graph, 0);

    }

​

    public static void addEdge(List<List<Integer>> graph, int u, int v) {

        graph.get(u).add(v);

        graph.get(v).add(u);

    }

​

    public static void bfs(List<List<Integer>> graph, int source) {

        int numVertices = graph.size();

        boolean[] visited = new boolean[numVertices];

        Queue<Integer> queue = new LinkedList<>();

​

        visited[source] = true;

        queue.add(source);

​

        while (!queue.isEmpty()) {

            int vertex = queue.poll();

            System.out.print(vertex + " ");

​

            for (int neighbor : graph.get(vertex)) {

                if (!visited[neighbor]) {

                    visited[neighbor] = true;

                    queue.add(neighbor);

                }

            }

        }

    }

}