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public class ReverseOddLevels {
    public TreeNode reverseOddLevels(TreeNode root) {
        if (root == null) return null;

        Queue<TreeNode> queue = new LinkedList<>();
        queue.offer(root);
        int level = 0; // Root is level 0

        while (!queue.isEmpty()) {
            int size = queue.size();
            List<TreeNode> currentLevelNodes = new ArrayList<>();

            for (int i = 0; i < size; i++) {
                TreeNode node = queue.poll();
                currentLevelNodes.add(node);

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

            // Reverse node values if level is odd
            if (level % 2 == 1) {
                int left = 0, right = currentLevelNodes.size() - 1;
                while (left < right) {
                    // Swap values of left and right nodes
                    int temp = currentLevelNodes.get(left).val;
                    currentLevelNodes.get(left).val = currentLevelNodes.get(right).val;
                    currentLevelNodes.get(right).val = temp;
                    left++;
                    right--;
                }
            }

            level++;
        }

        return root;
    }