Leetcode: Balanced Binary Tree @Python

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

class Solution:
    # @param root, a tree node
    # @return a boolean
    def subtreeMm(self, crt):
        if not crt:
            return True, 0
        lsp,rsp=self.subtreeMm(crt.left),self.subtreeMm(crt.right)
        if lsp[0] and rsp[0]:
            return [True, 1+max(lsp[1],rsp[1])] if abs(lsp[1]-rsp[1])<=1 else [False,0]
        else:
            return False,0
    def isBalanced(self, root):
        return self.subtreeMm(root)[0]