https://leetcode.com/problems/binary-tree-level-order-traversal-ii/

bin_tree_traverse.py

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution:
    def levelOrderBottom(self, root: 'TreeNode') -> 'List[List[int]]':
        if not root:
            return []
        q = [(root, 0)]
        r = {}
        i = 0
        while q:
            n, l = q.pop()
            if l in r:
                r[l].append(n.val)
            else:
                r[l] = [n.val]
            if n.right:
                q.append((n.right, l+1))
            if n.left:
                q.append((n.left, l+1))
        a = list(r.values())
        a.reverse()
        return a