```
class Solution(object):
def findLeaves(self, root):
"""
:type root: TreeNode
:rtype: List[List[int]]
"""
res = []
while(root is not None):
subList = []
root = self.helper(root, subList)
res.append(subList)
return res
def helper(self, root, res):
if root is None:
return
if root.left is None and root.right is None:
res.append(root.val)
return None
root.left = self.helper(root.left, res)
root.right = self.helper(root.right, res)
return root
```