Binary_Tree_Implementation _and_Traveral.java

public class BinaryTreesB {
    static class Node{
        int data;
        Node left;
        Node right;
        
        Node(int data)
        {
            this.data=data;
            this.left=null;
            this.right=null; 
        }
    }
        static class BinaryTree{
            static int idx=-1;
            public static Node buildTree(int nodes[])
            {
                idx++;
                if(nodes[idx]==-1)
                {
                    return null;
                }
                Node newNode =new Node(nodes[idx]);
                
                    newNode.left=buildTree(nodes);
                    newNode.right=buildTree(nodes);
                     
                return newNode;
                
            }
            public static void preorder(Node root)
            {
                if(root==null)
                    return;
            
            System.out.print(root.data+" ");
                preorder(root.left);
                preorder(root.right);
        }
             public static void inorder(Node root)
            {
                if(root==null)
                    return;
            
        
                inorder(root.left);
                  System.out.print(root.data+" ");
                inorder(root.right);
        }
             public static void postorder(Node root)
            {
                if(root==null)
                    return;
            
                postorder(root.left);
                postorder(root.right);
                System.out.print(root.data+" ");
        }
            
            public static void levelOrder(Node root)
            {
                if(root==null)
                    return;
                Queue<Node> q=new LinkedList<>();
                q.add(root);
                q.add(null);
                
                while(!q.isEmpty())
                {
                    Node currNode=q.remove();
                    if(currNode==null)
                    {
                        System.out.println();
                        if(q.isEmpty())
                        {
                            break;
                        }
                        else
                        {
                            q.add(null);
                        }
                    }
                    else
                    {
                        System.out.print(currNode.data+" ");
                        if(currNode.left != null)
                        {
                           q.add(currNode.left); 
                        }
                        if(currNode.right !=null)
                        {
                            q.add(currNode.right);
                        }
                    }
                }
            }
            
            public static int height(Node root)
            {
                if(root==null)
                    return 0;
                int lh =height(root.left);
                int rh=height(root.right);
                return Math.max(lh,rh)+1;
            }
        }
    
    public static void main(String[] args) {
        int nodes[]={1,2,4,-1,-1,5,-1,-1,3,-1,6,-1,-1};
        BinaryTree tree=new BinaryTree();
        Node root=tree.buildTree(nodes);
        System.out.println(root.data);
         System.out.print("Preorder : ");
        tree.preorder(root);
         System.out.print("Inorder : ");
        tree.inorder(root);
         System.out.print("Postorder : ");
        tree.postorder(root);
          System.out.println("Levelorder : ");
        tree.levelOrder(root);
         
    }
}