leetcode979

搞不定这种递归计算，可能我的头脑是“线性”的，这种一层一层的，想起来太费劲了，想的头发都没了。以后希望能有AI来写这种程序吧，AI不怕掉头发！

 1 class Solution(object):
 2     def __init__(self):
 3         self.res = 0
 4 
 5     def dfs(self,root):
 6         if not root: 
 7             return 0
 8         left = self.dfs(root.left)
 9         right = self.dfs(root.right)
10         self.res += abs(left) + abs(right)
11         return root.val + left + right - 1
12 
13     def distributeCoins(self, root: TreeNode) -> int:
14         self.dfs(root)
15         return self.res

参考：https://leetcode.com/problems/distribute-coins-in-binary-tree/discuss/221930/JavaC%2B%2BPython-Recursive-Solution