1 public class Solution {
2 public ArrayList<ArrayList<Integer>> levelOrder(TreeNode root) {
3 ArrayList<ArrayList<Integer>> res = new ArrayList<ArrayList<Integer>>();
4 LinkedList<TreeNode> cur = new LinkedList<TreeNode>();
5 if(root==null) return res;
6 cur.offer(root);
7 while(!cur.isEmpty()){
8 LinkedList<TreeNode> next = new LinkedList<TreeNode>();
9 ArrayList<Integer> sol = new ArrayList<Integer>();
10 for(TreeNode n :cur){
11 sol.add(n.val);
12 if(n.left!=null) next.offer(n.left);
13 if(n.right!=null) next.offer(n.right);
14 }
15 res.add(sol);
16 cur = next;
17 }
18 return res;
19 }
20 }
