102. Binary Tree Level Order Traversal

class Solution {
    public List<List<Integer>> levelOrder(TreeNode root) {
        List<List<Integer>> ans = new ArrayList<>();
        if(root == null){
            return ans;
        }
        Queue<TreeNode> check = new LinkedList<TreeNode>();
        check.add(root);
        while( check.size() > 0){
            List<Integer> temp = new ArrayList<>();
            System.out.println(check.size());
            int c = check.size();
            for(int i = 0;i < c; i++){
                root = check.remove();
                temp.add(root.val);
                 System.out.println("hi");
                if(root.left != null) check.add(root.left);
                if(root.right != null) check.add(root.right);
            }
            ans.add(temp);
        }
        return ans;
    }
}