Breadth First Search Algorithm in Java

Author: pratik1998

Diff for: BreadthFirstSearch/Java/BFS.java

@@ -0,0 +1,53 @@
+/* 
+ * Time-Complexity:- O(V+E)
+ * 
+ */
+
+
+import java.util.*;
+
+public class BFS {
+
+	static ArrayList<ArrayList<Integer>> graph;
+	static Queue<Integer> queue;
+	public static void traverse(int source)
+	{
+		queue = new LinkedList<>();
+		queue.add(source);
+		boolean[] visited = new boolean[graph.size()];
+		visited[source]=true;
+		while(!queue.isEmpty())
+		{
+			int q = queue.poll();
+			System.out.println(q);
+			ArrayList<Integer> list = graph.get(q);
+			for(int i=0;i<list.size();i++)
+			{
+				if(!visited[list.get(i)])
+				{
+					queue.add(list.get(i));
+					visited[list.get(i)] = true;
+				}
+			}
+		}
+	}
+	public static void main(String[] args) {
+		// TODO Auto-generated method stub
+		graph = new ArrayList<>();
+		Scanner sc = new Scanner(System.in);
+		int vertices = sc.nextInt();
+		int edges = sc.nextInt();
+		for(int i=0;i<vertices;i++)
+			graph.add(new ArrayList<>());
+		for(int i=0;i<edges;i++)
+		{
+			int u = sc.nextInt();
+			int v = sc.nextInt();
+			graph.get(u-1).add(v-1);
+			graph.get(v-1).add(u-1);
+		}
+		int source = sc.nextInt();
+		traverse(source-1);
+		sc.close();
+	}
+}