| 1 | class BFS { |
| 2 | public List<List<Integer>> levelOrder(TreeNode root) { |
| 3 | List<List<Integer>> result = new ArrayList<>(); |
| 4 | |
| 5 | if (root == null) { |
| 6 | return result; |
| 7 | } |
| 8 | |
| 9 | Queue<TreeNode> queue = new LinkedList<>(); |
| 10 | queue.offer(root); |
| 11 | |
| 12 | while (!queue.isEmpty()) { |
| 13 | int levelSize = queue.size(); |
| 14 | List<Integer> currentLevel = new ArrayList<>(levelSize); |
| 15 | for (int i=0; i < levelSize; i++) { |
| 16 | TreeNode currentNode = queue.poll(); |
| 17 | currentLevel.add(currentNode.val); |
| 18 | if (currentNode.left != null) { |
| 19 | queue.offer(currentNode.left); |
| 20 | } |
| 21 | if (currentNode.right != null) { |
| 22 | queue.offer(currentNode.right); |
| 23 | } |
| 24 | } |
| 25 | result.add(currentLevel); |
| 26 | } |
| 27 | return result; |
| 28 | } |
| 29 | |
| 30 | public List<Integer> rightSideView(TreeNode root) { |
| 31 | List<Integer> result = new ArrayList<>(); |