Performing Breadth First Search recursively

Question

Let\'s say you wanted to implement a breadth-first search of a binary tree recursively. How would you go about it?

Is it possible using only the call-stack

Answer 1

A simple BFS and DFS recursion in Java:
Just push/offer the root node of the tree in the stack/queue and call these functions.

public static void breadthFirstSearch(Queue queue) {

    if (queue.isEmpty())
        return;

    Node node = (Node) queue.poll();

    System.out.println(node + " ");

    if (node.right != null)
        queue.offer(node.right);

    if (node.left != null)
        queue.offer(node.left);

    breadthFirstSearch(queue);
}

public static void depthFirstSearch(Stack stack) {

    if (stack.isEmpty())
        return;

    Node node = (Node) stack.pop();

    System.out.println(node + " ");

    if (node.right != null)
        stack.push(node.right);

    if (node.left != null)
        stack.push(node.left);

    depthFirstSearch(stack);
}