import java.util.*;
public class Solution {
ArrayList<ArrayList<Integer> > Print(TreeNode pRoot) {
ArrayList<ArrayList<Integer>> result = new ArrayList();
Queue<TreeNode> queue = new LinkedList();
if(pRoot != null) {
queue.offer(pRoot);
}
while(!queue.isEmpty()) {
// 输出一层
int n = queue.size();
ArrayList<Integer> list = new ArrayList();
while(n-- > 0) {
TreeNode node = queue.poll();
list.add(node.val);
// 存入孩子并计数
if(node.left != null) {
queue.offer(node.left);
}
if(node.right != null) {
queue.offer(node.right);
}
}
result.add(list);
}
return result;
}
}