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| 1 | +package geeksForGeeks.binarySearchTree; |
| 2 | + |
| 3 | + |
| 4 | +// Java program to print BFS traversal from a given source vertex. |
| 5 | +// BFS(int s) traverses vertices reachable from s. |
| 6 | +import java.io.*; |
| 7 | +import java.util.*; |
| 8 | + |
| 9 | +// This class represents a directed graph using adjacency list |
| 10 | +// representation |
| 11 | +public class Graph |
| 12 | +{ |
| 13 | + private int V; // No. of vertices |
| 14 | + private LinkedList<Integer> adj[]; //Adjacency Lists |
| 15 | + |
| 16 | + // Constructor |
| 17 | + Graph(int v) |
| 18 | + { |
| 19 | + V = v; |
| 20 | + adj = new LinkedList[v]; |
| 21 | + for (int i=0; i<v; ++i) |
| 22 | + adj[i] = new LinkedList(); |
| 23 | + } |
| 24 | + |
| 25 | + // Function to add an edge into the graph |
| 26 | + void addEdge(int v,int w) |
| 27 | + { |
| 28 | + adj[v].add(w); |
| 29 | + } |
| 30 | + |
| 31 | + // prints BFS traversal from a given source s |
| 32 | + void BFS(int s) |
| 33 | + { |
| 34 | + // Mark all the vertices as not visited(By default |
| 35 | + // set as false) |
| 36 | + boolean visited[] = new boolean[V]; |
| 37 | + |
| 38 | + // Create a queue for BFS |
| 39 | + LinkedList<Integer> queue = new LinkedList<Integer>(); |
| 40 | + |
| 41 | + // Mark the current node as visited and enqueue it |
| 42 | + visited[s]=true; |
| 43 | + queue.add(s); |
| 44 | + |
| 45 | + while (queue.size() != 0) |
| 46 | + { |
| 47 | + // Dequeue a vertex from queue and print it |
| 48 | + s = queue.poll(); |
| 49 | + System.out.print(s+" "); |
| 50 | + |
| 51 | + // Get all adjacent vertices of the dequeued vertex s |
| 52 | + // If a adjacent has not been visited, then mark it |
| 53 | + // visited and enqueue it |
| 54 | + Iterator<Integer> i = adj[s].listIterator(); |
| 55 | + while (i.hasNext()) |
| 56 | + { |
| 57 | + int n = i.next(); |
| 58 | + if (!visited[n]) |
| 59 | + { |
| 60 | + visited[n] = true; |
| 61 | + queue.add(n); |
| 62 | + } |
| 63 | + } |
| 64 | + } |
| 65 | + } |
| 66 | + |
| 67 | + // Driver method to |
| 68 | + public static void main(String args[]) |
| 69 | + { |
| 70 | + Graph g = new Graph(4); |
| 71 | + |
| 72 | + g.addEdge(0, 1); |
| 73 | + g.addEdge(0, 2); |
| 74 | + g.addEdge(1, 2); |
| 75 | + g.addEdge(2, 0); |
| 76 | + g.addEdge(2, 3); |
| 77 | + g.addEdge(3, 3); |
| 78 | + |
| 79 | + System.out.println("Following is Breadth First Traversal "+ |
| 80 | + "(starting from vertex 2)"); |
| 81 | + |
| 82 | + g.BFS(2); |
| 83 | + } |
| 84 | +} |
| 85 | +// This code is contributed by Aakash Hasija |
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