| 1 | class Solution { |
| 2 | public List<List<Integer>> zigzagLevelOrder(TreeNode root) { |
| 3 | |
| 4 | List<List<Integer>> list = new ArrayList<List<Integer>>(); |
| 5 | |
| 6 | if(root == null) return list; |
| 7 | |
| 8 | boolean flag = true; |
| 9 | |
| 10 | Queue<TreeNode> queue = new LinkedList<TreeNode>(); |
| 11 | |
| 12 | queue.add(root); |
| 13 | |
| 14 | while(!queue.isEmpty()) |
| 15 | { |
| 16 | int level = queue.size(); |
| 17 | List<Integer> subList = new ArrayList<>(); |
| 18 | for(int i=0;i<level;i++) |
| 19 | { |
| 20 | if(queue.peek().left!=null) queue.add(queue.peek().left); |
| 21 | if(queue.peek().right!=null) queue.add(queue.peek().right); |
| 22 | if(flag==true) |
| 23 | { |
| 24 | subList.add(queue.remove().val); |
| 25 | } |
| 26 | else |
| 27 | { |
| 28 | subList.add(0,queue.remove().val); |
| 29 | } |
| 30 | } |
| 31 | flag = !flag; |
| 32 | list.add(subList); |
| 33 | } |
| 34 | return list; |
| 35 | |
| 36 | } |
| 37 | } |