Level order traversal

//Level order traversal

import java.util.LinkedList; 
import java.util.Queue; 
import java.io.*;
import java.util.*;

class Node{
    int data;
    Node left;
    Node right;
    Node(int data){
        this.data = data;
        left=null;
        right=null;
    }
}

class GfG {
    
    static Node buildTree(String str){
        
        if(str.length()==0 || str.charAt(0)=='N'){
            return null;
        }
        
        String ip[] = str.split(" ");
        // Create the root of the tree
        Node root = new Node(Integer.parseInt(ip[0]));
        // Push the root to the queue
        
        Queue<Node> queue = new LinkedList<>(); 
        
        queue.add(root);
        // Starting from the second element
        
        int i = 1;
        while(queue.size()>0 && i < ip.length) {
            
            // Get and remove the front of the queue
            Node currNode = queue.peek();
            queue.remove();
                
            // Get the current node's value from the string
            String currVal = ip[i];
                
            // If the left child is not null
            if(!currVal.equals("N")) {
                    
                // Create the left child for the current node
                currNode.left = new Node(Integer.parseInt(currVal));
                // Push it to the queue
                queue.add(currNode.left);
            }
                
            // For the right child
            i++;
            if(i >= ip.length)
                break;
                
            currVal = ip[i];
                
            // If the right child is not null
            if(!currVal.equals("N")) {
                    
                // Create the right child for the current node
                currNode.right = new Node(Integer.parseInt(currVal));
                    
                // Push it to the queue
                queue.add(currNode.right);
            }
            i++;
        }
        
        return root;
    }

    static void printInorder(Node root)
    {
        if(root == null)
            return;
            
        printInorder(root.left);
        System.out.print(root.data+" ");
        
        printInorder(root.right);
    }
    
	public static void main (String[] args) throws IOException{
	        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
	        
	        int t=Integer.parseInt(br.readLine());
    
	        while(t > 0){
	            String s = br.readLine();
    	    	  Node root = buildTree(s);
        	    Solution g = new Solution();
              ArrayList <Integer> res = g.levelOrder(root);

              for (Integer num : res) {
                  System.out.print(num + " ");
    			    }
              System.out.println();

              t--;            
        }
    }   
}

class Node
{
    int data;
    Node left, right;

    Node(int item)
    {
        data = item;
        left = right = null;
    }
}

class Solution
{
    //Function to return the level order traversal of a tree.
    static ArrayList <Integer> levelOrder(Node root) 
    {
        ArrayList<Integer> ans = new ArrayList<>();
        Queue<Node> queue = new LinkedList<>();
        queue.add(root);
        
        while(!queue.isEmpty()) {
            Node n = queue.remove();
            
            if(n.left != null) {
                queue.add(n.left);
            }
            
            if(n.right != null) {
                queue.add(n.right);
            }
            
            ans.add(n.data);
        }
        
        return ans;
    }
}