public List<List<Integer>> levelOrderBottom(TreeNode root) {
List<List<Integer>> result =new ArrayList();
List<TreeNode> list=new ArrayList();
if (root==null) return result;
list.add(root);
while (!list.isEmpty())
{
List<Integer> curlist =new ArrayList();
List<TreeNode> nextlist=new ArrayList();
for (TreeNode cur:list)
{
curlist.add(cur.val);
if(cur.left!=null) nextlist.add(cur.left);
if(cur.right!=null) nextlist.add(cur.right);
}
list = nextlist;
result.add(0,curlist); // 先近先出
}
return result;
}
