Level order traversal

leveltraversal.java

public ArrayList<Integer> levelorder(TreeNode root) {
      ArrayList<Integer> levelOrderedList = new ArrayList<Integer>();                        
      Queue<TreeNode> q = new LinkedList<TreeNode>();
      TreeNode curr = null;
      if(root == null) {
          return null;
      }
      q.add(root);
      while(!q.isEmpty()) {
          curr = (TreeNode)q.remove();
          //process current node
          levelOrderedList.add(curr.data);
          //System.out.print(curr.data);
          if(curr.left != null) {
              q.add(curr.left);
          }            
          if(curr.right != null) {
              q.add(curr.right);
          }
      } 
      return levelOrderedList;       
  }