BFSSearch

package org.example;

import java.util.*;

public class BFSSearch {

    public static void main(String[] args) {
        BFSGraph graph = new BFSGraph();
        graph.addVertex("A");
        graph.addVertex("B");
        graph.addVertex("C");
        graph.addVertex("D");
        graph.addVertex("E");
        graph.addVertex("F");
        graph.addVertex("G");

        graph.addEdge(new BFSGraph.BFSEdge("A", "B"));
        graph.addEdge(new BFSGraph.BFSEdge("A", "C"));
        graph.addEdge(new BFSGraph.BFSEdge("B", "D"));
        graph.addEdge(new BFSGraph.BFSEdge("B", "E"));
        graph.addEdge(new BFSGraph.BFSEdge("C", "F"));
        graph.addEdge(new BFSGraph.BFSEdge("E", "F"));
        graph.addEdge(new BFSGraph.BFSEdge("E", "G"));
        graph.addEdge(new BFSGraph.BFSEdge("F", "G"));

        System.out.println("BFS starting from vertex A:");
        graph.bfsSearch("A");
    }
}

class BFSGraph {

    private Map<String, List<BFSEdge>> adjVertices = new HashMap<>();

    void addVertex(String label) {
        adjVertices.putIfAbsent(label, new ArrayList<>());
    }

    void addEdge(BFSEdge edge) {
        adjVertices.get(edge.getFrom()).add(edge);
        adjVertices.get(edge.getTo()).add(new BFSEdge(edge.getTo(), edge.getFrom()));
    }

    Set<String> getVertices() {
        return adjVertices.keySet();
    }

    List<BFSEdge> getEdges(String label) {
        return adjVertices.get(label);
    }

    void bfsSearch(String start) {
        Set<String> visited = new HashSet<>();
        Queue<String> list = new LinkedList<>();
        list.add(start);
        while (!list.isEmpty()) {
            String vertex = list.poll();
            if (!visited.contains(vertex)) {
                visited.add(vertex);
                System.out.print(vertex + " ");
                List<BFSEdge> edgeList = adjVertices.get(vertex);
                if (edgeList != null) {
                    for (BFSEdge edge : edgeList) {
                        if (!visited.contains(edge.getTo())) {
                            list.add(edge.getTo());
                        }
                    }
                }
            }
        }
    }

    static class BFSEdge {
        private String from;
        private String to;

        public BFSEdge(String from, String to) {
            this.from = from;
            this.to = to;
        }

        public String getFrom() {
            return from;
        }

        public String getTo() {
            return to;
        }
    }
}