How to return a string with a Breadth First Order traversal of a binary search tree?

Question

So I've figured out how to do a bread-first order for a binary search tree but I need to return a String with a breadth-first order traversal of the tree, how do I do that?

My Code:

 /**
 * Returns a breadth-first order String of tree elements.
 * 
 * @return a String with a breadth-first order traversal of the tree
 */
public String breadthFirstOrder() {

    Queue<Node<E>> queue = new LinkedList<Node<E>>();

     if (root == null)
         System.out.println("Empty tree");
     queue.clear();
     queue.add(root);
     while(!queue.isEmpty()){
         Node<E> node = queue.remove();
         System.out.print(node.data + " ");
         if(node.left != null) queue.add(node.left);
         if(node.right != null) queue.add(node.right);
        }

}

Pass a StringBuilder in as a parameter and append to it as you visit each node during the BFS. — Jim Garrison
– Jim Garrison, Commented May 5, 2014 at 4:33

richard · Accepted Answer · 2014-05-05 04:47:38Z

1

just define a String variable and add the node.data to it while searching.

/**
 * Returns a breadth-first order String of tree elements.
 * 
 * @return a String with a breadth-first order traversal of the tree
 */
public String breadthFirstOrder() {

 Queue<Node<E>> queue = new LinkedList<Node<E>>();
 String traversal = "";
 if (root == null)
     System.out.println("Empty tree");
 queue.clear();
 queue.add(root);
 while(!queue.isEmpty()){
     Node<E> node = queue.remove();
     System.out.print(node.data + " ");
     traversal += node.data + " ";
     if(node.left != null) queue.add(node.left);
     if(node.right != null) queue.add(node.right);
    }
    return traversal;
}

edited May 5, 2014 at 4:47

answered May 5, 2014 at 4:40

richard

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5 Comments

user3602956 Over a year ago

I get an error on if(node.right != null) queue.add(node.rightjava and Node<E> node = queue*remove();

user3602956 Over a year ago

whats node.rightjava and whats with the queue*remove()?

richard Over a year ago

this time it should be ok.

user3602956 Over a year ago

Here's my test, is this what it's suppose to print out afterwards? multipleTree = new BinarySearchTree<Integer>(); multipleTree.add(100); multipleTree.add(50); multipleTree.add(150); multipleTree.add(75); multipleTree.add(25); multipleTree.add(125); multipleTree.add(175); assertEquals("100 50 150 25 75 125 175" , multipleTree.breadthFirstOrder());

richard Over a year ago

you can check your output info, it's the same as your print info, and I believe it's what you want.

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