PrintNodesAtKDistance.java

public class PrintNodesAtKDistance {
  public void print(Node root, int k) {
    if (root != null) {
      if (k == 0) {
        System.out.print(" " + root.data);
      }
      print(root.left, --k);
      print(root.right, k);
    }
  }

  public static void main(String[] args) throws java.lang.Exception {
    Node root = new Node(1);
    root.left = new Node(2);
    root.right = new Node(3);
    root.left.left = new Node(4);
    root.left.right = new Node(5);
    root.left.right.left = new Node(6);
    root.left.right.right = new Node(7);
    root.right.right = new Node(8);
    root.right.right.right = new Node(9);
    PrintNodesAtKDistance i = new PrintNodesAtKDistance();
    System.out.println("Nodes at 3 distance from root : ");
    i.print(root, 3);
  }
}

class Node {
  int data;
  Node left;
  Node right;

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