binary tree zigzag level order traversal

public List<List<Integer>> zigzagLevelOrder(TreeNode root) {
    List<List<Integer>> ans = new ArrayList<List<Integer>>();
    if (root == null)
        return ans;
    List<TreeNode> parents = new LinkedList<TreeNode>();
    parents.add(root);
    boolean right = true;
    while (parents.isEmpty() == false) {
        List<TreeNode> children = new LinkedList<TreeNode>();
        for (int i = 0 ; i < parents.size(); ++i) {
            root = parents.get(i);
            if (root.left != null)
                children.add(root.left);
            if (root.right != null)
                children.add(root.right);
        }
        List<Integer> temp = new ArrayList<Integer>();
        if (right) {
            for (int i = 0; i < parents.size(); ++i) {
                temp.add(parents.get(i).val);
            }
        } else {
            for (int i = parents.size() - 1; i >= 0; --i) {
                temp.add(parents.get(i).val);
            }
        }
        right = !right;
        ans.add(temp);
        parents = children;
    }
    return ans;
}